Endre søk
Begrens søket
1234567 51 - 100 of 480
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 51. Boqvist, S
    et al.
    Pettersson, H
    Svensson, Åke
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Andersson, Y
    Sources of sporadic Yersinia enterocilitica infection in children in Sweden, 2004: a case-control study2009Inngår i: Epidemiology and Infection, ISSN 0950-2688, E-ISSN 1469-4409, Vol. 137, s. 897-905Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     

    Young children account for a large proportion of reported

    Yersinia enterocolitica infections in Sweden with a high incidence compared with other gastrointestinal infections, such as salmonellosis and campylobacteriosis. A case-control study was conducted to investigate selected risk factors for domestic sporadic yersiniosis in children aged 0–6 years in Sweden. In total, 117 cases and 339 controls were included in the study. To minimize exclusion of observations due to missing data a multiple non-parametric imputation technique was used. The following risk factors were identified in the multivariate analysis : eating food prepared from raw pork products (OR 3.0, 95% CI 1.8–5.1) or treated sausage (OR 1.9, 95% CI 1.1–3.3), use of a baby’s dummy (OR 1.9, 95% CI 1.1–3.2) and contact with domestic animals (OR 2.0, 95% CI 1.2–3.4). We believe that the importance of Y. enterocolitica

    infection in children has been neglected and that results from this study can be used to develop preventive recommendations.

  • 52.
    Borenius, Gustaf
    Stockholms universitet.
    Hit probability in salvos and series1963Doktoravhandling, monografi (Annet vitenskapelig)
  • 53.
    Britton, Tom
    Stockholms universitet, Naturvetenskapliga fakulteten.
    Epidemics with heterogeneous mixing: stochastic models and statistical tests1996Doktoravhandling, med artikler (Annet vitenskapelig)
  • 54.
    Britton, Tom
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Ball, Frank
    An epidemic model with infector and exposure dependent severity2009Inngår i: Mathematical Biosciences, ISSN 0025-5564, E-ISSN 1879-3134, Vol. 218, nr 2, s. 105-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A stochastic epidemic model allowing for both mildly and severely infectious individuals is defined, where an individual can become severely infectious directly upon infection or if additionally exposed to infection. It is shown that, assuming a large community, the initial phase of the epidemic may be approximated by a suitable branching process and that the main part of an epidemic that becomes established admits a law of large numbers and a central limit theorem, leading to a normal approximation for the final outcome of such an epidemic. Effects of vaccination prior to an outbreak are studied and the critical vaccination coverage, above which only small outbreaks can occur, is derived. The results are illustrated by simulations that demonstrate that the branching process and normal approximations work well for finite communities, and by numerical examples showing that the final outcome may be close to discontinuous in certain model parameters and that the fraction mildly infected may actually increase as an effect of vaccination.

  • 55.
    Britton, Tom
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Lindholm, Mathias
    Uppsala universitet.
    Turova, Tatyana
    Lunds universitet.
    A dynamic network in a dynamic population: asymptotic properties2011Inngår i: Journal of Applied Probability, ISSN 0021-9002, E-ISSN 1475-6072, Vol. 48, s. 1163-1178Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We derive asymptotic properties for a stochastic dynamic network model in a stochastic dynamic population. In the model, nodes give birth to new nodes until they die, each node being equipped with a social index given at birth. During the life of a node it creates edges to other nodes, nodes with high social index at higher rate, and edges disappear randomly in time. For this model, we derive a criterion for when a giant connected component exists after the process has evolved for a long period of time, assuming that the node population grows to infinity. We also obtain an explicit expression for the degree correlation rho (of neighbouring nodes) which shows that rho is always positive irrespective of parameter values in one of the two treated submodels, and may be either positive or negative in the other model, depending on the parameters.

  • 56.
    Britton, Tom
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Neal, Peter
    University of Manchester.
    The time to extinction for an SIS-household-epidemic model2010Inngår i: Journal of Mathematical Biology, ISSN 0303-6812, E-ISSN 1432-1416, Vol. 61, nr 6, s. 763-769Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyse a Markovian SIS epidemic amongst a finite population partitioned into households. Since the population is finite, the epidemic will eventually go extinct, i.e., have no more infectives in the population. We study the effects of population size and within household transmission upon the time to extinction. This is done through two approximations. The first approximation is suitable for all levels of within household transmission and is based upon an Ornstein-Uhlenbeck process approximation for the diseases fluctuations about an endemic level relying on a large population. The second approximation is suitable for high levels of within household transmission and approximates the number of infectious households by a simple homogeneously mixing SIS model with the households replaced by individuals. The analysis, supported by a simulation study, shows that the mean time to extinction is minimized by moderate levels of within household transmission.

  • 57.
    Britton, Tom
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Trapman, Pieter
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Maximizing the size of the giant2012Inngår i: Journal of Applied Probability, ISSN 0021-9002, E-ISSN 1475-6072, Vol. 49, nr 4, s. 1156-1165Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Consider a random graph where the mean degree is given and fixed. In this paper we derive the maximal size of the largest connected component in the graph. We also study the related question of the largest possible outbreak size of an epidemic occurring 'on' the random graph (the graph describing the social structure in the community). More precisely, we look at two different classes of random graphs. First, the Poissonian random graph in which each node i is given an independent and identically distributed (i.i.d.) random weight X-i with E(X-i) = mu, and where there is an edge between i and j with probability 1 - e(-XiXj/(mu n)), independently of other edges. The second model is the thinned configuration model in which then vertices of the ground graph have i.i.d. ground degrees, distributed as D, with E(D) = mu. The graph of interest is obtained by deleting edges independently with probability 1 - p. In both models the fraction of vertices in the largest connected component converges in probability to a constant 1 - q, where q depends on X or D and p. We investigate for which distributions X and D with given mu and p, 1 - q is maximized. We show that in the class of Poissonian random graphs, X should have all its mass at 0 and one other real, which can be explicitly determined. For the thinned configuration model, D should have all its mass at 0 and two subsequent positive integers.

  • 58. Broberg, Per
    et al.
    Miller, Frank
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Conditional estimation in two-stage adaptive designs2017Inngår i: Biometrics, ISSN 0006-341X, E-ISSN 1541-0420, Vol. 73, nr 3, s. 895-904Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider conditional estimation in two-stage sample size adjustable designs and the consequent bias. More specifically, we consider a design which permits raising the sample size when interim results look rather promising, and which retains the originally planned sample size when results look very promising. The estimation procedures reported comprise the unconditional maximum likelihood, the conditionally unbiased Rao-Blackwell estimator, the conditional median unbiased estimator, and the conditional maximum likelihood with and without bias correction. We compare these estimators based on analytical results and a simulation study. We show how they can be applied in a real clinical trial setting.

  • 59.
    Bruce, Daniel
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Optimal Design and Inference for Correlated Bernoulli Variables using a Simplified Cox Model2008Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis proposes a simplification of the model for dependent Bernoulli variables presented in Cox and Snell (1989). The simplified model, referred to as the simplified Cox model, is developed for identically distributed and dependent Bernoulli variables.

    Properties of the model are presented, including expressions for the loglikelihood function and the Fisher information. The special case of a bivariate symmetric model is studied in detail. For this particular model, it is found that the number of design points in a locally D-optimal design is determined by the log-odds ratio between the variables. Under mutual independence, both a general expression for the restrictions of the parameters and an analytical expression for locally D-optimal designs are derived.

    Focusing on the bivariate case, score tests and likelihood ratio tests are derived to test for independence. Numerical illustrations of these test statistics are presented in three examples. In connection to testing for independence, an E-optimal design for maximizing the local asymptotic power of the score test is proposed.

    The simplified Cox model is applied to a dental data. Based on the estimates of the model, optimal designs are derived. The analysis shows that these optimal designs yield considerably more precise parameter estimates compared to the original design. The original design is also compared against the E-optimal design with respect to the power of the score test. For most alternative hypotheses the E-optimal design provides a larger power compared to the original design.

  • 60.
    Bruce, Daniel
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Some Properties for a Simplified Cox Binary Model2007Inngår i: Communications in statistics: Theory and methodsArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a simplification of the model for dependent Bernoulli variables presented in Cox and Snell (1989). The new model referred to as the simplified Cox model is developed for identically distributed and dependent binary variables. Properties of the model are presented, including expressions for the log-likelihood function and the Fisher information. Under mutual independence, a general expression for the restrictions of the parameters are derived. The simplified Cox is illustrated using a data set from a clinical trial.

  • 61.
    Bruce, Daniel
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Some properties for a simplified Cox binary model2008Inngår i: Communications in Statistics - Theory and Methods, ISSN 0361-0926, E-ISSN 1532-415X, Vol. 37, nr 16, s. 2606-2616Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article proposes a simplification of the model for dependent binary variables presented in Cox and Snell (1989). The new model referred to as the simplified Cox model is developed for identically distributed and dependent binary variables. Properties of the model are presented, including expressions for the log-likelihood function and the Fisher information. Under mutual independence, a general expression for the restrictions of the parameters are derived. The simplified Cox model is illustrated using a data set from a clinical trial.

  • 62.
    Bruce, Daniel
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Nyquist, Hans
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Testing for dependency of Bernoulli variables2007Inngår i: International Journal of Statistical Sciences, ISSN 1683-5603, Vol. 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this paper is to derive test procedures for studies where data consist of pairs of Bernoulli variables. Applications exist in, for example, ophthalmology and studies on matched pairs. Score tests and likelihood ratio tests are derived for testing the dependency between the Bernoulli variables. Multinomial logit models are used to incorporate explanatory variables. Test statistics for two particular models are thoroughly outlined. Numerical illustrations of these test statistics are presented in three examples, including one with visual impairment data.

  • 63.
    Bueno, Edgar
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    A comparison of Stratified simple random sampling and Probability proportional-to-size sampling2018Rapport (Annet vitenskapelig)
    Abstract [en]

    The sampling strategy that couples probability proportional-to-size sampling with the GREG estimator has sometimes been called "optimal", as it minimizes the anticipated variance. This optimality, however, relies on the assumption that the finite population of interest can be seen as a realization of a superpopulation model that is known to the statistician. Making use of the same model, the strategy that couples model-based stratification with the GREG estimator is an alternative that, although theoretically less efficient, has shown to be sometimes more efficient than the so-called optimal from an empirical point of view. We compare the two strategies from both analytical and simulation standpoints and show that optimality is not robust towards misspecications of the model. In fact gross errors may be observed when a misspecified model is used.

  • 64. Bystrova, Ksenia
    et al.
    Ivanova, Valentina
    Edhborg, Maigun
    Matthiesen, Ann-Sofi
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Ransjo-Arvidson, Anna-Berit
    Mukhamedrakhimov, Rifkat
    Uvnas-Moberg, Kerstin
    Widstrom, Ann-Marie
    Early Contact versus Separation: Effects on Mother-Infant Interaction One Year Later2009Inngår i: Birth, ISSN 0730-7659, E-ISSN 1523-536X, Vol. 36, nr 2, s. 97-109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: A tradition of separation of the mother and baby after birth still persists in many parts of the world, including some parts of Russia, and often is combined with swaddling of the baby. The aim of this study was to evaluate and compare possible long-term effects on mother-infant interaction of practices used in the delivery and maternity wards, including practices relating to mother-infant closeness versus separation. Methods: A total of 176 mother-infant pairs were randomized into four experimental groups: Group I infants were placed skin-to-skin with their mothers after birth, and had rooming-in while in the maternity ward. Group II infants were dressed and placed in their mothers' arms after birth, and roomed-in with their mothers in the maternity ward. Group III infants were kept in the nursery both after birth and while their mothers were in the maternity ward. Group IV infants were kept in the nursery after birth, but roomed-in with their mothers in the maternity ward. Equal numbers of infants were either swaddled or dressed in baby clothes. Episodes of early suckling in the delivery ward were noted. The mother-infant interaction was videotaped according to the Parent-Child Early Relational Assessment (PCERA) 1 year after birth. Results: The practice of skin-to-skin contact, early suckling, or both during the first 2 hours after birth when compared with separation between the mothers and their infants positively affected the PCERA variables maternal sensitivity, infant's self-regulation, and dyadic mutuality and reciprocity at 1 year after birth. The negative effect of a 2-hour separation after birth was not compensated for by the practice of rooming-in. These findings support the presence of a period after birth (the early ""sensitive period"") during which close contact between mother and infant may induce long-term positive effect on mother-infant interaction. In addition, swaddling of the infant was found to decrease the mother's responsiveness to the infant, her ability for positive affective involvement with the infant, and the mutuality and reciprocity in the dyad. Conclusions: Skin-to-skin contact, for 25 to 120 minutes after birth, early suckling, or both positively influenced mother-infant interaction 1 year later when compared with routines involving separation of mother and infant.

  • 65. Camitz, Martin
    et al.
    Svensson, Åke
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    The effect of time distribution shape on a complex epidemic model2009Inngår i: Bulletin of Mathematical Biology, ISSN 0092-8240, E-ISSN 1522-9602, Vol. 71, nr 8, s. 1902-1913Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In elaborating a model of the progress of an epidemic, it is necessary to make assumptions about the distributions of latency times and infectious times. In many models, the often implicit assumption is that these times are independent and exponentially distributed. We explore the effects of altering the distribution of latency and infectious times in a complex epidemic model with regional divisions connected by a travel intensity matrix. We show a delay in spread with more realistic latency times. More realistic infectiousness times lead to faster epidemics. The effects are similar but accentuated when compared to a purely homogeneous mixing model.

  • 66.
    Cano, Raul
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    On the efficiency of the Bayesian bootstrap1992Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The efficiency of the Bayesian bootstrap is treated for large and small samples from infinite and finite populations. The Bayesian bootstrap is compared with nonparametric and parametric Bayesian methods in the infinite case, for large samples and considering the mean and truncation functionals. It is shown that in this case, all these methods give the same results in a first order asymptotical sense. However, when the Bayesian bootstrap is compared with a parametric method in the truncation case, a inefficiency is detected. An expression of this inefficiency is given in terms of the Fisher information. A method to measure the bootstrap efficiency for small samples is proposed and its feasibility is illustrated. Some ways of improving this efficiency are considered. In the finite case, known results of the Bayesian approach are summarized. The Bayesian bootstrap feasibility is demonstrated by means of a real-life estimation problem. Next, the Bayesian bootstrap in the presence of outliers is also investigated. Some alternative methods based on the Bayesian bootstrap resampling technique are also considered. The efficiency of all these methods with respect to a parametric Bayesian method is studied in a simulated lognormal population. Finally, the Bayesian bootstrap and modified versions of the previous methods are compared in a population generated from real data.

  • 67.
    Carlson, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    A Per-Record Risk of Disclosure Using a Poisson-Inverse Gaussian Regression Model2002Rapport (Annet vitenskapelig)
    Abstract [en]

    Per-record measures of disclosure risk have potential uses in statistical disclosure control programs as a means of identifying sensitive or atypical records in public-use microdata files. A measure intended for sample data based on the Poisson-inverse Gaussian distribution and overdispersed log-linear modeling is presented. An empirical example indicates that the proposed model performs approximately as well as the Poisson-lognormal model of Skinner and Holmes (1998) and may be a tractable alternative as the required computational effort is significantly smaller. It is also demonstrated how to extend the application to take into account population level information. The empirical results indicate that using population level information sharpens the risk measure.

  • 68.
    Carlson, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    An Empirical Comparison of Some Methods for Disclosure Risk Assessment2002Rapport (Annet vitenskapelig)
    Abstract [en]

    With the release of public-use microdata filles it is important to assess the risk of disclosing individual information. A measure of disclosure risk often considered in the literature is the proportion of unique records in the file that are also unique in the population. Various methods based on superpopulation models have been proposed for estimating this quantity using sample data. An empirical comparison of a selection of models applied to three real-life data sets is presented. The general conclusion is that no one model is uniformly best with respect to the risk measure used and that performance varies greatly between di¤erent types of data.

  • 69.
    Carlson, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    An Empirical Comparison of Some Methods for Disclosure Risk Assessment2005Konferansepaper (Annet vitenskapelig)
  • 70.
    Carlson, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Assessing Microdata Disclosure Risk Using the Poisson-Inverse Guassian Distribution2002Inngår i: Statistics In Transition, ISSN 1234-7655, Vol. 5, nr 6, s. 901-925Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An important measure of identification risk associated with the release of microdata or large complex tables is the number or proportion of population units that can be uniquely identified by some set of characterizing attributes which partition the population into subpopulations or cells. Various methods for estimating this quantity based on sample data have been proposed in the literature by means of superpopulation models. In the present paper the Poisson- inverse Gaussian (PiG) distribution is proposed as a possible approach within this context. Disclosure risk measures are discussed and derived under the proposed model as are various methods of estimation. An example on real data is given and the results indicate that the PiG model may be a useful alternative to other models.

  • 71.
    Carlson, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    On Assessing Disclosure Risk in Microdata2002Inngår i: Contributions to Social Network Analysis, INformation Theory and Other Topics in Statistics: A Festschrift in Honour of Ove Frank on the Occasion of His 65th Birthday / [ed] Jan Hagberg, Stockholm: Department of Statistics, Stockholm University , 2002, 1, s. 202-213Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 72.
    Carlson, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Reliabilitetsanalys av Bedömningsinstrument för Pedagogiskt och Socialt Klimat (PESOK) i skolor2004Rapport (Annet vitenskapelig)
    Abstract [sv]

    Denna rapport är en redovisning av en reliabilitetsanalys som gjorts på uppdrag av Grosin & McNamara HB, avseende ett mätinstrument för att bedöma det pedagogiska och sociala klimatet (PESOK) i skolor. Mätinstrumentet är i form av ett webbaserat frågeformulär och har utvecklats av uppdragsgivarna, se McNamara (1999, 2004). De items som bygger upp instrumentet har a priori delats in i grupper av items för att aggregera till s.k. faktormedelvärden. Den metod som huvudsakligen har använts för att skatta reliabilitetskoefficienterna är Cronbach’s alfa och besläktade mått. Principalkomponentanalys och explorativ faktoranalys har kompletterat analysen tillsammans med annan beskrivande statistik; de förra metoderna har avsett att undersöka antalet latenta faktorer bakom grupperna av items.

    Den huvudsakliga slutsatsen är att de olika grupperingarna i faktorer uppvisar relativt sett goda egenskaper med avseende på reliabilitet med undantag för enstaka grupper. Vissa metodologiska och teoretiska problem har också noterats. Bland annat att data har en hierarkisk struktur med individer vid skolorna som uppgiftslämnare. Dessa individdata aggregeras sedan till medelvärden för hela skolan som sedan är tänkta att användas som kollektiva egenskaper för de enskilda skolorna och det är dessa aggregerade värdens egenskaper ur relibilitetsperspektiv som har varit föremål för analysen.

  • 73.
    Carlson, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Some Contributions to Statistical Disclosure Control2002Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    An important issue associated with the release of statistical data, is the possibility of disclosing individual information about respondents. Statistical disclosure control (SDC), is the discipline that deals with methods of producing statistical data that are safe enough to be released while retaining its analytical value and also methods of assessing the disclosures risks. This thesis deals with both aspects.

    In the first paper, a method for limiting disclosure risks in microdata (individual data) is described. The method is a variant of so-called data-swapping and is intended to be applied to quantitative data and is based on the rank structure of the original data. Theoretical results and simulation studies indicate that the method performs at least reasonably well when applied to bivariate normal data. An important measure of identification risk associated with the release of microdata or large complex tables is proportion of population units that can be uniquely identified by a set of matchable attributes. In the second paper a model based on the Poisson-inverse Gaussian distribution is proposed as a possible approach within this context. Disclosure risk measures are discussed and derived under the proposed model as are various methods of estimation. The results indicate that the model may be a useful and analytically tractable alternative to other models. The third paper reports the results of an empirical comparison between different methods of assessing file-level disclosure risk as measured by the estimated number of unique population units amongst unique records and the number of unique units in the population. The results indicate that no one model or method performs uniformly best and that performance varies greatly between different types of data. The fourth and last paper presents a method for assessing a per-record measure of disclosure risk based on a Poisson-inverse Gaussian regression model. Per-record measures may be used to identify sensitive (atypical) records in a file which can be modified separately using SDC techniques prior to the release. The method builds on loglinear modelling and is exemplified using both sample and population level information. The results indicate that the model provides a tractable alternative to the Poisson-lognormal model and that using population level information sharpens the measure.

  • 74.
    Carlson, Michael
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen. Statistiska centralbyrån, Statistics Sweden.
    Jansson, Ingegerd
    Statistiska centralbyrån, Statistics Sweden.
    Lindkvist, Helen
    Statistiska centralbyrån, Statistics Sweden.
    Bridging the Gap Between Theory and Practice: Experiences from Statistics Sweden in Applying SDC Methodology2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Statistics Sweden has identified a need to increase the level of knowl-edge in the SDC field among methodologists and also to develop a unified view and strategy on application of SDC methodology. A project was thus initiated with the goal to spread knowledge but also to collate current practices and ex-periences within the agency. The project resulted in a course on SDC given at Statistics Sweden and this paper provides a brief first report on the work so far, reviewing the background and describing the course and possible future activities. Furthermore, several practical examples were discussed during the course, two of which are briefly described here; the Industrial production index and Structure of wages and earnings in the private sector.

  • 75.
    Carlson, Michael
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Jansson, Ingegerd
    Statistiska centralbyrån, Statistics, Sweden.
    Lundquist, Peter
    Statistiska centralbyrån, Statistics Sweden.
    Lack-of-Balance and R-indicators As Measures of Utility in Statistical Disclosure Control2013Inngår i:  , 2013Konferansepaper (Annet vitenskapelig)
  • 76.
    Carlson, Michael
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Nyquist, HansStockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.Villani, MattiasStockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Official statistics: methodology and applications in honour of Daniel Thorburn2010Collection/Antologi (Annet vitenskapelig)
    Abstract [en]

    This book comprises articles on the methodology and applications of official statistics written by some of the best scholars and methodologists in the Nordic-Baltic region to celebrate Professor Daniel THorburn on his 65th birthday. The book's eighteen chapters span a wide spectrum of topics in official statistics, including its foundational aspects, sampling designs, survey methodology, index construction, and methods for registers and adminstrative data.

  • 77.
    Carlson, Michael
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Salabasis, Mickael
    Dep. of Economic Statistics, Stockholm School of Economics.
    A Data-Swapping Technique for Generating Synthetic Samples: A Method for Disclosure Control1998Inngår i: International Seminar on New Techniques and Technologies for Statistics : Pre-proceedings : 4-6 November, 1998, Sorrento, Italy, Sorrento: Eurostat; ISTAT , 1998, s. 109-114Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A data-swapping technique based on ranks for generating synthetic data sets suitable for dissemination is presented. The method is mainly intended to be applied to quantative data down to at least an ordinal scale although it should be applicable in other cases as well. Generalizations and variations of the proposed method are briefly discussed. The expected performance is investigated by means of simulation studies and an analytical result is stated. The results from the simulations studies indicate that the proposed method performs reasonably well in the bivariate normal case when the correlation coefficient is used as the measure of association between pairs of variables.

  • 78.
    Carlson, Michael
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Salabasis, Mickael
    A data-swapping technique using ranks: a method for disclosure control2002Inngår i: Research in Official Statistics, ISSN 1023-098X, Vol. 6, nr 2, s. 35-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A data-swapping technique based on ranks is described and suggested as a possible approach to statistical disclosure control. The proposed method is intended to be applied to quantitative data and utilises the rank structure of disjoint subsets of an original data set; values of one subset are exchanged for values of other subsets. The procedure retains the validity of a sample on an intra-variate level but the association between pairs of variables is typically weakened. Theoretical and simulation results indicate that the proposed method performs reasonably well in the bivariate normal case.

  • 79.
    Cederlöf, Rune
    Stockholms universitet.
    The twin method in epidemiological studies on chronic disease.1966Doktoravhandling, monografi (Annet vitenskapelig)
  • 80.
    Chimanga, Taurai
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Interest Rate Derivatives: An analysis of interest rate hybrid products2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The globilisation phenomena is causing an increasing interaction between different markets and sectors. This has led to the evolution of derivative instruments from ”single asset” instruments to complex derivatives that have underlying assets from different markets, sectors and sub-sectors. These are the so-called hybrid products that have multi-assets as underlying instruments. This article focuses on interest rate hybrid products. In this article an analysis of the application of stochastic interest rate models and stochastic volatility models in pricing and hedging interest rate hybrid products will be explored.

  • 81. Christensen, Sören
    et al.
    Lindensjö, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    On time-inconsistent stopping problems and mixed strategy stopping timesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A game-theoretic framework for time-inconsistent stopping problems where the time-inconsistency is due to the consideration of a non-linear function of an expected reward is developed. A class of mixed strategy stopping times that allows the agents in the game to choose the intensity function of a Cox process is introduced. A subgame perfect Nash equilibrium is defined. The equilibrium is characterized and other results with different necessary and sufficient conditions for equilibrium are proven. This includes a smooth fit result. A mean-variance problem and a variance problem are studied as examples. The state process is a general one-dimensional Itô diffusion.

  • 82.
    Corander, Jukka
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    On Bayesian graphical model determination2000Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A graphical model specifies a graph representation of the independence structure of a multivariate distribution, where nodes represent variables and edges association between variables.

    This thesis introduces methodology for determination of graphical models for multivariate distributions within the exponential family. Model determination is understood in the present context as quantification of the uncertainty about the association structure, given empirical observations. Only models with symmetric associations between variables are considered. The distributions investigated are multinomial, multinormal and conditional Gaussian (CG) distributions. Local graphical models which generalize the graphical loglinear models for multinomial distributions are introduced. These models allow conditional associations to be absent locally, in parts of the sample space.

    A unifying theme is that the models are represented in terms of affine restrictions to the parameters of a regular exponential model. All introduced methods are applicable to the complete class of graphical models, consisting of both decomposable and non-decomposable models. Various real data sets investigated earlier in the graphical modeling literature are used to illustrate the methods.

    Two different measures of model uncertainty are considered: the posterior probability and the relative expected utility of a model. Posterior probabilities are estimated by a Markov chain Monte Carlo sampling method. The other measure of model uncertainty is derived in a decision theoretic framework under reference priors for the model parameters.

    The expected logarithmic utility of a model is decomposed into predictive performance and relative cost. The predictive performance is measured by posterior expectation of the negative entropy of the distribution induced by a graphical model. This expectation has an analytic expression for decomposable models, while a simulation consistent estimate can be obtained for non-decomposable models. The expected logarithmic utility is asymptotically equivalent to the Schwarz criterion under a certain cost function.

  • 83. Corander, Jukka
    et al.
    Koski, Timo
    Pavlenko, Tatjana
    Tillander, Annika
    Karolinska Institutet, Sweden.
    Bayesian Block-Diagonal Predictive Classifier for Gaussian Data2013Inngår i: Synergies of Soft Computing and Statistics for Intelligent Data Analysis / [ed] Rudolf Kruse, Michael R. Berthold, Christian Moewes, María Ángeles Gil, Przemysław Grzegorzewski, Olgierd Hryniewicz, Springer Berlin/Heidelberg, 2013, s. 543-551Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The paper presents a method for constructing Bayesian predictive classifier in a high-dimensional setting. Given that classes are represented by Gaussian distributions with block-structured covariance matrix, a closed form expression for the posterior predictive distribution of the data is established. Due to factorization of this distribution, the resulting Bayesian predictive and marginal classifier provides an efficient solution to the high-dimensional problem by splitting it into smaller tractable problems. In a simulation study we show that the suggested classifier outperforms several alternative algorithms such as linear discriminant analysis based on block-wise inverse covariance estimators and the shrunken centroids regularized discriminant analysis.

  • 84. Dahmström, Karin
    Some binary response situations: theory and applications1980Doktoravhandling, med artikler (Annet vitenskapelig)
  • 85.
    Dalén, Jörgen
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Price measurement and index construction: some contributions to theory and application1995Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Four different problems are treated, all concerned with problems arising when compiling price indexes in official statistics. One deals with the computation of so called elementary aggregates, low level indexes for single products, when proper weights for the observations are not available. The second part treats different options for applying hedonic indexes. The third report concerns variance estimation, i.e. computing margins of error due to sampling for a consumer price index. Finally, the fourth part analyses different sources of error in a consumer price index and proposes a model structure for aggregating these errors. An overview (in Swedish) over current topics in index construction introduces this volume.

  • 86.
    Deijfen, Maria
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Hirscher, Timo
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Lopes, Fabio
    Competing frogs on Z2019Inngår i: Electronic Journal of Probability, ISSN 1083-6489, E-ISSN 1083-6489, Vol. 24, artikkel-id 146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A two-type version of the frog model on Z^d is formulated, where active type i particles move according to lazy random walks with probability p_i of jumping in each time step (i = 1; 2). Each site is independently assigned a random number of particles. At time 0, the particles at the origin are activated and assigned type 1 and the particles atone other site are activated and assigned type 2, while all other particles are sleeping. When an active type i particle moves to a new site, any sleeping particles there are activated and assigned type i, with an arbitrary tie-breaker deciding the type if the site is hit by particles of both types in the same time step. Let G_i denote the event that type i activates infinitely many particles. We show that the events G_1 intersect G_2^c and G_1^c intersect G_2 both have positive probability for all p_1,p_2 in (0,1]. Furthermore, if p_1 = p_2, then the types can coexist in the sense that the event G_1 intersect G_2 has positive probability. We also formulate several open problems. For instance, we conjecture that, when the initial number of particles per site has a heavy tail, the types can coexist also when p_1 not equal p_2.

  • 87.
    Deijfen, Maria
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen. Matematisk statistik.
    Häggström, Olle
    The two-type Richardson model with unbounded initial configurations2007Inngår i: Annals of Applied Probability, Vol. 17, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The two-type Richardson model describes the growth of two competing infections on Z^d and the main question is whether both infection types can simultaneously grow to occupy infinite parts of Z^d. For bounded initial configurations, this has been thoroughly studied. In this paper, an unbounded initial configuration consisting of points x=(x_1,...,x_d) in the hyperplane H={x in Z^d: x_1=0} is considered. It is shown that, starting from a configuration where all points in H\{0} are type 1 infected and the origin 0 is type 2 infected, there is a positive probability for the type 2 infection to grow unboundedly if and only if it has a strictly larger intensity than the type 1 infection. If instead the initial type 1 infection is restricted to the negative x_1-axis, it is shown that the type 2 infection at the origin can grow unboundedly also when the infection types have the same intensity.

  • 88.
    Deijfen, Maria
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Kets, Willemien
    Random intersection graphs with tunable degree distribution and clustering2007Rapport (Annet vitenskapelig)
    Abstract [en]

    A random intersection graph is constructed by independently assigning each vertex a subset of a given set and drawing an edge between two vertices if and only if their respective subsets intersect. In this paper a model is developed in which each vertex is given a random weight, and vertices with larger weights are more likely to be assigned large subsets. The distribution of the degree of a given vertex is determined and is shown to depend on the weight of the vertex. In particular, if the weight distribution is a power law, the degree distribution will be so as well. Furthermore, an asymptotic expression for the clustering in the graph is derived. By tuning the parameters of the model, it is possible to generate a graph with arbitrary clustering, expected degree and - in the power law case - tail exponent.

  • 89.
    Deijfen, Maria
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Lopes, Fabio M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Bipartite Stable Poisson Graphs on R2012Inngår i: Markov processes and related fields, ISSN 1024-2953, Vol. 18, nr 4, s. 583-594Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Let red and blue points be distributed on R according to two independent Poisson processes R and B and let each red (blue) point independently be equipped with a random number of half-edges according to a probability distribution nu (mu). We consider translation-invariant bipartite random graphs with vertex classes defined by the point sets of R, and B, respectively, generated by a scheme based on the Gale - Shapley stable marriage for perfectly matching the half-edges. Our main result is that, when all vertices have degree 2, then the resulting graph almost surely does not contain an infinite component. The two-color model is hence qualitatively different from the one-color model, where Deijfen, Holroyd and Peres have given strong evidence that there is an infinite component. We also present simulation results for other degree distributions.

  • 90.
    Deijfen, Maria
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    van der Hofstad, Remco
    Hooghiemstra, Gerard
    Scale-free percolation2013Inngår i: Annales de l'I.H.P. Probabilites et statistiques, ISSN 0246-0203, E-ISSN 1778-7017, Vol. 49, nr 3, s. 817-838Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We formulate and study a model for inhomogeneous long-range percolation on Z(d). Each vertex x is an element of Z(d) is assigned a non-negative weight W-x, where (W-x)(x is an element of Zd) are i.i.d. random variables. Conditionally on the weights, and given two parameters alpha, lambda > 0, the edges are independent and the probability that there is an edge between x and y is given by p(xy) = 1 - exp{-lambda WxWY/vertical bar x - y vertical bar(alpha)}. The parameter lambda is the percolation parameter, while a describes the long-range nature of the model. We focus on the degree distribution in the resulting graph, on whether there exists an infinite component and on graph distance between remote pairs of vertices. First, we show that the tail behavior of the degree distribution is related to the tail behavior of the weight distribution. When the tail of the distribution of W-x is regularly varying with exponent tau - 1, then the tail of the degree distribution is regularly varying with exponent gamma = alpha (tau - 1)/d. The parameter gamma turns out to be crucial for the behavior of the model. Conditions on the weight distribution and gamma are formulated for the existence of a critical vale lambda(c) is an element of (0, infinity) such that the graph contains an infinite component when lambda > lambda(c) and no infinite component when lambda > lambda(c). Furthermore, a phase transition is established for the graph distances between vertices in the infinite component at the point gamma = 2, that is, at the point where the degrees switch from having finite to infinite second moment. The model can be viewed as an interpolation between long-range percolation and models for inhomogeneous random graphs, and we show that the behavior shares the interesting features of both these models.

  • 91.
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Effects of water system uncertainties on effectiveness and efficiency of environmental policy and management2007Inngår i: International Workshop on Uncertainty in Environmental Modelling, Earth Sciences Centre, Uppsala University, 28-30 March, 2007, 2007Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Increasing water pollution and deterioration of aquatic ecosystems are serious environmental problems. Modelling of pollutant transport, mass transfer, attenuation and downstream loading, from various pollutant sources, along different hydrological pathways, to water recipients, is needed for relevant decisions on effective allocation of pollution abatement measures. However, it is for various reasons (measurement and monitoring gaps; scientifically unresolved modelling disagreements; large, irregular and deterministically unquantifiable or unpredictable natural variability) both difficult and uncertain to quantify the real effects of upstream pollutant emission changes on downstream pollutant loads and concentrations. Furthermore, it may also be highly uncertain which pollutant load and concentration level reductions that are necessary and sufficient for achieving good water quality and ecosystem status in different water environments. These uncertainties may have large effects on pollution abatement that need to be recognized and handled in environmental policy. We discuss here how the water system uncertainty effects may be set in a wider decision making context, by quantifying their implications for both the probability of success and the economic performance of different environmental policies and management strategies.

  • 92.
    Dominicus, Annica
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Latent variable models for longitudinal twin data2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Longitudinal twin data provide important information for exploring sources of variation in human traits. In statistical models for twin data, unobserved genetic and environmental factors influencing the trait are represented by latent variables. In this way, trait variation can be decomposed into genetic and environmental components. With repeated measurements on twins, latent variables can be used to describe individual trajectories, and the genetic and environmental variance components are assessed as functions of age. This thesis contributes to statistical methodology for analysing longitudinal twin data by (i) exploring the use of random change point models for modelling variance as a function of age, (ii) assessing how nonresponse in twin studies may affect estimates of genetic and environmental influences, and (iii) providing a method for hypothesis testing of genetic and environmental variance components. The random change point model, in contrast to linear and quadratic random effects models, is shown to be very flexible in capturing variability as a function of age. Approximate maximum likelihood inference through first-order linearization of the random change point model is contrasted with Bayesian inference based on Markov chain Monte Carlo simulation. In a set of simulations based on a twin model for informative nonresponse, it is demonstrated how the effect of nonresponse on estimates of genetic and environmental variance components depends on the underlying nonresponse mechanism. This thesis also reveals that the standard procedure for testing variance components is inadequate, since the null hypothesis places the variance components on the boundary of the parameter space. The asymptotic distribution of the likelihood ratio statistic for testing variance components in classical twin models is derived, resulting in a mixture of chi-square distributions. Statistical methodology is illustrated with applications to empirical data on cognitive function from a longitudinal twin study of aging.

  • 93.
    Ekheden, Erland
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Catastrophe, Ruin and Death - Some Perspectives on Insurance Mathematics2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis gives some perspectives on insurance mathematics related to life insurance and / or reinsurance. Catastrophes and large accidents resulting in many lost lives are unfortunatley known to happen over and over again. A new model for the occurence of catastrophes is presented; it models the number of catastrophes, how many lives that are lost, how many lost lives that are insured by a specific insurer and the cost of the resulting claims, this  makes it possible to calculate the price of reinsurance contracts linked to catastrophic events. 

    Ruin is the result if claims exceed inital capital and the premiums collected by an insurance company. We analyze the Cramér-Lundberg approximation for the ruin probability and give an explicit rate of convergence in the case were claims are bounded by some upper limit.

    Death is known to be the only thing that is certain in life. Individual life spans are however random, models for and statistics of mortality are imortant for, amongst others, life insurance companies whose payments ultimatley depend on people being alive or dead. We analyse the stochasticity of mortality and perform a variance decomposition were the variation in mortality data is either explained by the covariates age and time, unexplained systematic variation or random noise due to a finite population. We suggest a mixed regression model for mortality and fit it to data from the US and Sweden, including prediction intervals of future mortalities.

  • 94.
    Ekheden, Erland
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Hössjer, Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Analysis of the Stochasticity of Mortality Using Variance Decomposition2014Inngår i: Modern Problems in Insurance Mathematics / [ed] Dmitri Silvestrov and Anders Martin-Löf, Springer Publishing Company, 2014, s. 199-222Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    We analyse the stochasticity in mortality data from the USA, the UK and Sweden, and in particular to which extent mortality rates are explained by systematic variation, due to various risk factors, and random noise. We formalise this in terms of a mixed regression model with a logistic link function, and decomposethe variance of the observations into three parts: binomial risk, the variance due to random mortality variation in a finite population, systematic risk explained by the covariates and unexplained systematic risk, variance that comes from real changes in mortality rates, not captured by the covariates. The fraction of unexplained variance caused by binomial risk provides a limit in terms of the resolution that can be achieved by a model. This can be used as a model selection tool for selecting the number of covariates and regression parameters of the deterministic part of the regression function, and for testing whether unexplained systematic variation should be explicitly modelled or not. We use a two-factor model with ageand calendar year as covariates, and perform the variance decomposition for a simple model with a linear time trend on the logit scale. The population size turns out to be crucial, and for Swedish data, the simple model works surprisingly well, leaving only a small fraction of unexplained systematic risk, whereas for the UK and the USA, the amount of unexplained systematic risk is larger, so that more elaborate models might work better.

  • 95.
    Ekheden, Erland
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Hössjer, Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Multivariate Time Series Modeling, Estimation and Prediction of MortalitiesArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We introduce a mixed regression model for morality data whichcan be decomposed into a deterministic trend component explainedby the covariates age and calendar year, a multivariate Gaussian timeseries part not explained by the covariates, and binomial risk. Datacan be analyzed by means of a simple logistic regression model whenthe multivariate Gaussian time series component is absent and there isno overdispersion, as in Ekheden and Hössjer (2014). In this paper werather allow for overdispersion and the mixed regression model is ttedto mortality data from the United States and Sweden, with the aim toprovide prediction and condence intervals for future mortality, as wellas smoothing historical data, using the best linear unbiased predictor.We nd that the form of the Gaussian time series has a large impact onthe width of the prediction intervals, and it poses some new questionson proper model selection.

  • 96.
    Ekheden, Erland
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Hössjer, Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Pricing catastrophe risk in life (re)insurance2014Inngår i: Scandinavian Actuarial Journal, ISSN 0346-1238, E-ISSN 1651-2030, Vol. 2014, nr 4, s. 352-367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    What is the catastrophe risk a life insurance company faces? What is the correct price of a catastrophe cover? During a review of the current standard model, due to Strickler, we found that this model has some serious shortcomings. We therefore present a new model for the pricing of catastrophe excess of loss cover (Cat XL). The new model for annual claim cost C is based on a compound Poisson processof catastrophe costs. To evaluate the distribution of the cost of each catastrophe, we use the Peaks Over Threshold model for the total number of lost lives in each catastrophe and the beta binomial model for the proportion of these corresponding to customers of the insurance company. To be able to estimate the parameters of the model, international and Swedish data were collected and compiled,listing accidents claiming at least twenty and four lives, respectively. Fitting the new model to data, we find the fit to be good. Finally we give the price of a Cat XL contract and perform a sensitivity analysis of how some of the parameters affect the expected value and standard deviation of the cost and thus the price.

  • 97.
    Elofsson, Gunilla
    Stockholms universitet.
    Skattning av parametrar i en modell med känt linjärt funktionellt samband och konstanta variationskoefficienter med tillämpning på arbetstidsmätning.1970Doktoravhandling, monografi (Annet vitenskapelig)
  • 98. Elofsson, Stig
    On truncated sequential tests of parameters in various Poisson models with applications to traffic accidents1975Doktoravhandling, monografi (Annet vitenskapelig)
  • 99.
    Engsner, Hampus
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Multi-period valuation of insurance liabilities subject to capital requirements2018Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In the papers presented here, approaches to multi-period valuation of a liability cashflow in runoff, subject to repeated capital requirements, are developed and analyzed. The valuation approaches are inspired by current risk-based regulatory frameworks for the insurance industry, and consistent with the fundamental principles underlying them. The capital requirements are partly financed by capital providers with limited liability, meaning that the capital providers cannot lose more than the provided capital. Limited liability is an essential ingredient in the considered multi-period valuation framework.

    In the first paper, multi-period cost-of-capital valuation is considered. The liability value is defined in terms of the capital provider's criterion for accepting to provide capital which gives rise to a backward recursion from which the liability value can be computed. Explicit solutions to the recursion are obtained when the cashflows can be expressed in terms of multivariate Gaussian distributions.

    The second paper recognizes that due to limited liability (an option to default) the cashflow to the capital provider can be seen as that of a financial derivative instrument with optionality. Arbitrage-free valuation of this cashflow, similar to the valuation of so-called American type contingent claims, forms the basis of the multi-period approach to liability cashflow valuation considered here. The issue of selection of a replicating portfolio for offsetting the hedgeable part of the liability cashflow is investigated.

    The first two papers consider cashflows and valuations at a fixed set of times to be interpreted as the years from current time until the runoff of the liability is complete. In the third paper, the valuation and cashflow times are allowed to be arbitrary in the form of an arbitrary partition of the entire runoff period. The focus here is to properly define and analyze the effects of letting the mesh of the partition tend to zero, exploring the continuous-time value processes that appear.

  • 100.
    Engsner, Hampus
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Lindensjö, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Lindskog, Filip
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    The value of a liability cash flow in discrete time subject to capital requirements2020Inngår i: Finance and Stochastics, ISSN 0949-2984, E-ISSN 1432-1122, Vol. 24, nr 1, s. 125-167Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this paper is to define the market-consistent multi-period value of an insurance liability cash flow in discrete time subject to repeated capital requirements, and explore its properties. In line with current regulatory frameworks, the presented approach is based on a hypothetical transfer of the original liability and a replicating portfolio to an empty corporate entity, whose owner must comply with repeated one-period capital requirements but has the option to terminate the ownership at any time. The value of the liability is defined as the no-arbitrage price of the cash flow to the policyholders, optimally stopped from the owner’s perspective, taking capital requirements into account. The value is computed as the solution to a sequence of coupled optimal stopping problems or, equivalently, as the solution to a backward recursion.

1234567 51 - 100 of 480
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf