Change search
Refine search result
56789 351 - 400 of 402
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 351.
    Urioste, Jorge I
    et al.
    Sveriges lantbruksuniversitet, Uppsala.
    Franzén, Jessica
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Strandberg, Erling
    Sveriges lantbruksuniversitet, Uppsala.
    Relationships of novel somatic cell count traits with clinical mastitis using weekly observations2010Conference paper (Refereed)
  • 352.
    Villani, Mattias
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    A Bayesian approach to restrictions on the cointegration space2000Report (Other academic)
  • 353.
    Villani, Mattias
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Aspecte of Bayesian Cointegration2000Doctoral thesis, comprehensive summary (Other academic)
  • 354.
    Villani, Mattias
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Steady-state priors for vector autoregressions2009In: Journal of applied econometrics (Chichester, England), ISSN 0883-7252, E-ISSN 1099-1255, Vol. 24, no 4, p. 630-650Article in journal (Refereed)
    Abstract [en]

    Bayesian priors are often used to restrain the otherwise highly over-parameterized vector autoregressive (VAR) models. The currently available Bayesian VAR methodology does not allow the User to specify prior beliefs about the unconditional mean, or steady state, of the system. This is unfortunate as the Steady State is something that economists usually Claim to know relatively well. This paper develops easily implemented methods for analyzing both stationary and cointegrated VARs, in reduced or structural form, with an informative prior oil the steady state. We document that prior information on the steady state leads to substantial gains in forecasting accuracy Oil Swedish macro data. A second example illustrates, the use of informative steady-state priors in a cointegration model of the consumption-wealth relationship in the USA. 

  • 355.
    Villani, Mattias
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Kohn, Robert
    Giordani, Paolo
    Regression density estimation using smooth adaptive Gaussian mixtures2009In: Journal of Econometrics, ISSN 0304-4076, E-ISSN 1872-6895, Vol. 153, no 2, p. 155-173Article in journal (Refereed)
    Abstract [en]

    We model a regression density flexibly so that at each value of the covariates the density is a mixture of normals with the means, variances and mixture probabilities of the components changing smoothly as a function of the covariates. The model extends the existing models in two important ways. First, the components are allowed to be heteroscedastic regressions as the standard model with homoscedastic regressions can give a poor fit to heterciscedastic data, especially when the number of covariates is large. Furthermore, we typically need fewer components, which makes it easier to interpret the model and speeds up the computation. The second main extension is to introduce a novel variable selection prior into all the components of the model. The variable selection prior acts as a self-adjusting mechanism that prevents overfitting and makes it feasible to fit flexible high-dimensional surfaces. We use Bayesian inference and Markov Chain Monte Carlo methods to estimate the model. Simulated and real examples are used to show that the full generality of our model is required to fit a large class of densities, but also that special cases of the general model are interesting models for economic data.

  • 356.
    von Rosen, Tatjana
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    A Short Note on Matrices Used in Statistics2015In: Festschrift in Honor of Hans Nyquist on the occasion of his 65th birthday / [ed] Ellinor Fackle-Fornius, Stockholm: Department of Statistics, Stockholm University , 2015, p. 116-125Chapter in book (Other academic)
    Abstract [en]

    Matrices find many applications in various research areas and reallifeproblems. In spite of the availability of many innovative tools instatistics, the main tool of the applied statistician remains the linearmodel. Patterned matrices are often used to model dependence structureof longitudinal or repeated measures data. In this paper, someproperties of symmetric circular Toeplitz matrices will be outlined whichare useful for inference in linear models. Special focus is on block matriceshaving Kronecker structure since they arise in many applicationsfor modelling spatio-temporal data.

  • 357.
    von Rosen, Tatjana
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Evaluating the Quality of the Master’s Program in Statistics: a Study of the Curriculum Effect on the Quality of Students' Master Theses2018In: Looking back, looking forward: Proceedings of the Tenth International Conference on Teaching Statistics / [ed] M. A. Sorto, A. White, L. Guyot, Kyoto, Japan; Voorburg, The Netherlands: The International Statistical Institute, 2018Conference paper (Refereed)
    Abstract [en]

    In 2012, the Swedish Higher Education Authority evaluated the quality of the Master's Program in Statistics with a main focus on the students' master theses. In this work, the course outcomes of all master students (N=55) registered at the Stockholm University, between 2012 and 2017, were used to investigate whether a particular practice at the department that can be characterized by program syllabus, supervision, teachers' expertise, is associated with the quality of master theses, or the quality has been mostly affected by student related characteristics. The obtained results showed significant effect of the course results in Inference, Statistical Computations and Multivariate Analysis. No significant effects of student’s gender and age have been found however the supervisor’s effect turned to be significant.

  • 358.
    von Rosen, Tatjana
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    On the Inverse of Certain Patterned Matrices with Kronecker Product Structures2009Report (Other academic)
    Abstract [en]

    In this paper we derive explicit expressions for the entries of the inverse of a patternedmatrix that is a sum of Kronecker products. This matrix keeps the Kronecker structure under matrixinversion. We also obtain a closed form inverse in terms of block matrices.

  • 359.
    von Rosen, Tatjana
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    On the inverse of certain patterned sums of matrices with Kronecker product structures2011In: Linear and multilinear algebra, ISSN 0308-1087, E-ISSN 1563-5139, Vol. 59, no 5, p. 595-606Article in journal (Refereed)
    Abstract [en]

    In this article, we derive explicit expressions for the entries of the inverse of a patterned matrix that is a sum of Kronecker products. This matrix keeps the Kronecker structure under matrix inversion, and it is used, for example, in statistics, in particular in the linear mixed model analysis. The obtained results present new and extended existing algorithms for the inversion of the considered patterned matrices. We also obtain a closed-form inverse in terms of block matrices.

  • 360.
    von Rosen, Tatjana
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Peer assessment as active learning method2014In: ICOTS-9 Conference Proceedings / [ed] Katie Makar, Bruno de Sousa, Robert Gould, Auckland: International Association for Statistical Education (IASE) , 2014Conference paper (Refereed)
    Abstract [en]

    The importance of feedback in the student learning process is well understood among educational researchers (theorists) and teachers (practitioners). Its positive effects on the students learning and achievements have extensively been discussed in the theoretical research and illustrated by many empirical studies. It is also recognized that student assessment of other students’ work is a useful tool for activating student engagement in the learning process. This work presents the results of a pilot study investigating the attitudes toward peer-assessment of examination papers and exploring experiences of the peer-assessment process of students pursuing a bachelor degree in statistics.

  • 361.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Tamm, Ann E.
    Department of Sports Medicine and Rehabilitation, University of Tartu, Estonia.
    Tamm, A O
    Clinic of Internal Medicine, University of Tartu, Estonia.
    Traat, I
    Institute of mathematical statistics, University of Tartu, Estonia.
    Statistical Study of Factors Affecting Knee Joint Space and Osteophytes in the Population with Early Knee Osteoarthritis2013In: Multivariate Statistics: Theory and Applications: Proceedings of IX Tartu Conference on Multivariate Statistics and XX International Workshop on Matrices and StatisticsTartu, Estonia, 26 June – 1 July 2011 / [ed] Tõnu Kollo, Singapore: World Scientific, 2013, Vol. 16, no 2, p. 141-156Chapter in book (Refereed)
    Abstract [en]

    Two basic components of the radiographically measured knee osteoarthritis (KOA), joint space width (JSW) and size of osteophytes (OPH), were studied in order to characterize early stage of KOA and to reveal additional aspects of grading it. The study was conducted in 161 individuals (100 women and 61 men, 34{54 years old). A linear mixed and a generalized linear models were used to identify risk factors for JSW and OPH. Accounting for intra- and inter-knee correlations in these models is novel for knee studies. We obtained that at the early stage of KOA, JSW is more constitutionrelated, while the appearance of OPH more disease-related. The e®ect of gender on JSW was su±ciently large to establish di®erent de¯nitions of KOA for genders. In this case attention should be paid to the medial compartment as the narrower one. Our ¯ndings also suggested that the height of women could be taken into account when grading KOA, and that the imbalance between knee and thigh circumferences refers to the presence of OPH.

  • 362.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, D.
    On Estimation in Some Reduced Rank Extended Growth Curve Models2017In: Mathematical Methods of Statistics, ISSN 1066-5307, E-ISSN 1934-8045, Vol. 26, no 4, p. 299-310Article in journal (Refereed)
    Abstract [en]

    The general multivariate analysis of variance model has been extensively studied in the statistical literature and successfully applied in many different fields for analyzing longitudinal data. In this article, we consider the extension of this model having two sets of regressors constituting a growth curve portion and a multivariate analysis of variance portion, respectively. Nowadays, the data collected in empirical studies have relatively complex structures though often demanding a parsimonious modeling. This can be achieved for example through imposing rank constraints on the regression coefficient matrices. The reduced rank regression structure also provides a theoretical interpretation in terms of latent variables. We derive likelihood based estimators for the mean parameters and covariance matrix in this type of models. A numerical example is provided to illustrate the obtained results.

  • 363.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, Dietrich
    Bilinear regression with random effects and reduced rank restrictions2019In: Japanese journal of statistics and data science, ISSN 2520-8756Article in journal (Refereed)
    Abstract [en]

    Bilinear models with three types of effects are considered: fixed effects, random effects and latent variable effects. In the literature, bilinear models with random effects and bilinear models with latent variables have been discussed but there are no results available when combining random effects and latent variables. It is shown, via appropriate vector space decompositions, how to remove the random effects so that a well-known model comprising only fixed effects and latent variables is obtained. The spaces are chosen so that the likelihood function can be factored in a convenient and interpretable way. To obtain explicit estimators, an important standardization constraint on the random effects is assumed to hold. A theorem is presented where a complete solution to the estimation problem is given.

  • 364.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, Dietrich
    Explicit estimators in unbalanced mixed linear models2015In: Festschrift in honor of professor Ghazi Shukur on the occasion of his 60th birthday / [ed] Thomas Holgersson, Växjö: Linnaeus University Press, 2015, p. 121-125Chapter in book (Other academic)
    Abstract [en]

    The general unbalanced mixed linear model is considered. Throughresampling it is shown how the fixed effects can explicitly be estimated.The obtained estimator is non-linear but unbiased.

  • 365.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, Dietrich
    The Department of Energy and Technology, SLU, Sweden.
    On a class of singular nonsymmetric matrices with nonnegative integer spectra2010In: Algebraic methods in statistics and probability II: AMS Special Session Algebraic Methods in Statistics and Probability, March 27-29, 2009, University of Illinois at Urbana-Champaign, Champaign, IL / [ed] Marlos A.G. Viana, Henry P. Wynn, Providence, R.I.: American Mathematical Society , 2010, Vol. 516, p. 319-325Chapter in book (Other academic)
  • 366.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, Dietrich
    Small area estimation using reduced rank regression models2019In: Communications in Statistics - Theory and Methods, ISSN 0361-0926, E-ISSN 1532-415XArticle in journal (Refereed)
    Abstract [en]

    Small area estimation techniques have got a lot of attention during the last decades due to their important applications in survey studies. Mixed linear models and reduced rank regression analysis are jointly used when considering small area estimation. Estimates of parameters are presented as well as prediction of random effects and unobserved area measurements.

  • 367.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, Dietrich
    Institutionen för biometri och teknik, Sveriges lantbruksuniversitet, (SLU).
    Using a special Vandermonde matrix to generate a class ofsingular nonsymmetric matrices with nonnegative integerspectra2009Report (Other academic)
    Abstract [en]

    This paper presents a simple derivation of eigenvalues, and left andright eigenvectors of a square nonsymmetric matrix with remarkablefeatures. The proof is based on a special Vandermonde matrix. Thematrix appears in sampling theory, and its properly normalized righteigenvectors give the inclusion probabilities.

  • 368.
    von Rosen, Tatjana
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, Dietrich
    Volaufova, Julia
    A new method for obtaining explicit estimators in unbalanced mixed linear models2020In: Statistical papers, ISSN 0932-5026, E-ISSN 1613-9798, Vol. 61, no 1, p. 371-383Article in journal (Refereed)
    Abstract [en]

    The general unbalanced mixed linear model with two variance components is considered. Through resampling it is demonstrated how the fixed effects can be estimated explicitly. It is shown that the obtained nonlinear estimator is unbiased and its variance is also derived. A condition is given when the proposed estimator is recommended instead of the ordinary least squares estimator.

  • 369.
    Wahlund, Björn
    et al.
    Department of Clinical Neuroscience, Division of Psychiatry, Karolinska Institutet, Karolinska Hospital Huddinge, Stockholm, Sweden..
    Klonowski, Wlodzimierz
    Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland..
    Stepien, Paweł
    Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland..
    Stepien, Robert
    Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw..
    von Rosen, Tatjana
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    von Rosen, Dietrich
    The Department of Energy and Technology, SLU, Sweden.
    EEG data, fractal dimension and multivariate statistics2010In: Journal of Computer Science and Engineering, ISSN 2043-9091, Vol. 3, no 1, p. 10-16Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to discuss the concept of Inverse Problem, i.e. how to obtain information via data about a complex mathematical model. We propose that by merging ideas from applied mathematics with ideas from multivariate statistical inference it is possible to find solutions or good approximation of many complex scientific problems.

  • 370.
    Wegmann, Bertil
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Bayesian Comparison of Private and Common Values in Structural Second-Price AuctionsManuscript (preprint) (Other academic)
    Abstract [en]

    We compare the performance of the Gaussian second-price common value (CV) model in Wegmann and Villani (2011) to a comparable independent private value (IPV) version of that model. The two models are contrasted on a dataset from $1050$ Internet coin auctions at eBay. The models are evaluated along several dimensions, such as parameter inference, in-sample fit, and accuracy of out-of-sample predictive density forecasts. Both models fit the eBay data well with a slight edge for the more robust CV model. We do not find any evidence of a winner's curse effect in the eBay data, which speaks in favor of the IPV model. However, the optimal minimum bids in the CV model are clearly closer to the actual minimum bids in the eBay data than the optimal choice of no minimum bid in the IPV model. The IPV model predicts auction prices slightly better in most auctions, while the CV model is much better at predicting auction prices in more unusual auctions. The robustness of the CV model is also supported by a small simulation study, where the CV model performs relatively better on simulated data from the IPV model than the IPV model fitted to CV data.

  • 371.
    Wegmann, Bertil
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Bayesian Inference in Structural Second-Price Auctions2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis is to develop efficient and practically useful Bayesian methods for statistical inference in structural second-price auctions. The models are applied to a carefully collected coin auction dataset with bids and auction-specific characteristics from one thousand Internet auctions on eBay. Bidders are assumed to be risk-neutral and symmetric, and compete for a single object using the same game-theoretic strategy. A key contribution in the thesis is the derivation of very accurate approximations of the otherwise intractable equilibrium bid functions under different model assumptions. These easily computed and numerically stable approximations are shown to be crucial for statistical inference, where the inverse bid functions typically needs to be evaluated several million times.

    In the first paper, the approximate bid is a linear function of a bidder's signal and a Gaussian common value model is estimated. We find that the publicly available book value and the condition of the auctioned object are important determinants of bidders' valuations, while eBay's detailed seller information is essentially ignored by the bidders. In the second paper, the Gaussian model in the first paper is contrasted to a Gamma model that allows intrinsically non-negative common values. The Gaussian model performs slightly better than the Gamma model on the eBay data, which we attribute to an almost normal or at least symmetrical distribution of valuations. The third paper compares the model in the first paper to a directly comparable model for private values. We find many interesting empirical regularities between the models, but no strong and consistent evidence in favor of one model over the other. In the last paper, we consider auctions with both private-value and common-value bidders. The equilibrium bid function is given as the solution to an ordinary differential equation, from which we derive an approximate inverse bid as an explicit function of a given bid. The paper proposes an elaborate model where the probability of being a common value bidder is a function of covariates at the auction level. The model is estimated by a Metropolis-within-Gibbs algorithm and the results point strongly to an active influx of both private-value and common-value bidders.

  • 372.
    Wegmann, Bertil
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Bayesian Inference in Structural Second-Price Auctions with both Private-Value and Common-Value BiddersManuscript (preprint) (Other academic)
    Abstract [en]

    Auctions with asymmetric bidders have been actively studied in recent years. Tan and Xing (2011) show the existence of monotone pure-strategy equilibrium in auctions with both private-value and common-value bidders. The equilibrium bid function is given as the solution to an ordinary differential equation (ODE). We approximate the ODE and obtain a very accurate, approximate inverse bid as an explicit function of a given bid. This results in fast and numerically stable likelihood evaluations, which is an extremely valuable property for inference. We propose a model where the valuations of both common-value and private-value bidders are functions of covariates. The probability of being a common-value bidder is modeled by a logistic regression model with Bayesian variable selection. The model is estimated on a dataset of eBay coin auctions. We analyze the model using Bayesian methods implemented via a Metropolis-within-Gibbs algorithm. The posterior inference of the common-value part of the model is similar to the ones obtained from a model with only common-value bidders, whereas the private-value part of the model is more affected by the introduction of common-value bidders. There is on average a slightly larger probability for a bidder to be a common-value bidder, but this probability depends very little on the auction-specific covariates.

  • 373.
    Wegmann, Bertil
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Bayesian Inference in Structural Second-Price Auctions with Gamma Distributed Common ValuesManuscript (preprint) (Other academic)
    Abstract [en]

    Our paper explores possible limitations of the Gaussian model in Wegmann and Villani (2011) due to intrinsically non-negative values. The relative performance of the Gaussian model is compared to an extension of the Gamma model in Gordy (1998) within the symmetric second price common value model. A key feature in our approach is the derivation of an accurate approximation of the bid function for the Gamma model, which can be inverted and differentiated analytically. This is extremely valuable for fast and numerically stable evaluations of the likelihood function. The general MCMC algorithm in WV is utilized to estimate WV's eBay dataset from $1000$ auctions of U.S. proof coin sets, as well as simulated datasets from the Gamma model with different degrees of skewness in the value distribution. The Gaussian model fits the data slightly better than the Gamma model for the particular eBay dataset, which can be explained by the fairly symmetrical value distribution. The superiority of the Gamma to the Gaussian model is shown to increase for higher degrees of skewness in the simulated datasets.

  • 374.
    Wegmann, Bertil
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Bid function approximations of second price common value auctions2007Report (Other academic)
    Abstract [en]

    Se RR 2007:4

  • 375.
    Wegmann, Bertil
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics. Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Villani, Mattias
    Stockholm University, Faculty of Social Sciences, Department of Statistics. Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Bayesian Inference and Variable Selection in Structural Second Price Common: Value Auctions2008Report (Other (popular science, discussion, etc.))
    Abstract [en]

    Se internetadress: http://gauss.stat.su.se/rr/RR 2008_1.pdf

  • 376.
    Wegmann, Bertil
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Villani, Mattias
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Bayesian Inference in Structural Second-Price Common Value Auctions2011In: Journal of business & economic statistics, ISSN 0735-0015, E-ISSN 1537-2707, Vol. 29, no 3, p. 382-396Article in journal (Refereed)
    Abstract [en]

    Structural econometric auction models with explicit game-theoretic modeling of bidding strategies have been quite a challenge from a methodological perspective, especially within the common value framework. We develop a Bayesian analysis of the hierarchical Gaussian common value model with stochastic entry introduced by Bajari and Hortacsu. A key component of our approach is an accurate and easily interpretable analytical approximation of the equilibrium bid function, resulting in a fast and numerically stable evaluation of the likelihood function. We extend the analysis to situations with positive valuations using a hierarchical gamma model. We use a Bayesian variable selection algorithm that simultaneously samples the posterior distribution of the model parameters and does inference on the choice of covariates. The methodology is applied to simulated data and to a newly collected dataset from eBay with bids and covariates from 1000 coin auctions. We demonstrate that the Bayesian algorithm is very efficient and that the approximation error in the bid function has virtually no effect on the model inference. Both models fit the data well, but the Gaussian model outperforms the gamma model in an out-of-sample forecasting evaluation of auction prices. This article has supplementary material online.

  • 377. Welderufael, B. G.
    et al.
    De Koning, D. J.
    Fikse, W. F.
    Strandberg, E.
    Franzén, Jessica
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Christensen, O. F.
    Genetic evaluation of mastitis liability and recovery through longitudinal models of simulated SCC2013In: Book of Abstracts of the 64th Annual Meeting of the European Federation of Animal Science, Wageningen Academic Publishers, 2013, p. 522-522Conference paper (Refereed)
  • 378. Welderufael, B. G.
    et al.
    de Koning, D. J.
    Janss, L.
    Franzén, Jessica
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Fikse, W. F.
    Longitudinal Analysis of Somatic Cell Count for Joint Genetic Evaluation of Mastitis and Recovery Liability2014In: Proceedings, 10th World Congress of Genetics Applied to Livestock Production, 2014, article id 095Conference paper (Refereed)
    Abstract [en]

    Better models of genetic evaluation for mastitis can be developed through longitudinal analysis of somatic cell count (SCC) which usually is used as a proxy for mastitis. Mastitis and recovery data with weekly observations of SCC were simulated for daughter groups of 60 and 240 per sire. Data were created to define cases: 1 if SCC was above a pre-specified boundary, else 0. A transition from below to above the boundary indicates probability to contract mastitis, and the other way indicates recovery. The MCMCglmm package was used to estimate breeding values. In the 60 daughters group, accuracies ranged from 0.53 to 0.54 for mastitis and 0.22 to 0.23 for recovery. Whereas, in the 240 daughters group accuracies ranged from 0.83 to 0.85 for mastitis and 0.57 to 0.65 for recovery. Reasonable accuracies can be achieved from SCC based estimates.

  • 379. Welderufael, B. G.
    et al.
    de Koning, D. J.
    Janss, L. L. G.
    Franzen, Jessica
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Fikse, W. F.
    Simultaneous genetic evaluation of simulated mastitis susceptibility and recovery ability using a bivariate threshold sire model2016In: Acta agriculturae Scandinavica. Section A, Animal science, ISSN 0906-4702, E-ISSN 1651-1972, Vol. 66, no 3, p. 125-134Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to develop a new approach for joint genetic evaluation of mastitis and recovery. Two mastitis incidences (0.28 and 0.95) measured via somatic cell count and three between traits genetic correlations (0.0, 0.2, and -0.2) were simulated for daughter group sizes of 60 and 240. A transition model was applied to model transitions between healthy and disease state. The RJMC package in DMU was used to estimate (co)variances. Heritabilities were consistent with the simulated value (0.039) for susceptibility and a bit upward biased for recovery. Estimates of genetic correlations were -0.055, 0.205, and -0.192 for the simulated values of 0.0, 0.2, and -0.2, respectively. For daughter group size of 60, accuracies of sire EBV ranged from 0.56 to 0.69 for mastitis and from 0.26 to 0.48 for recovery. The study demonstrated that both traits can be modeled jointly and simulated correlations could be correctly reproduced.

  • 380. Welderufael, Berihu
    et al.
    De Koning, Dirk-Jan
    Fikse, Freddy
    Strandberg, Erling
    Franzén, Jessica
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Christensen, O. F.
    Genetic Evaluation of Mastistis Liability and Recovery through Longitudinal Models of SCC2013Conference paper (Refereed)
  • 381. Welderufael, Berihu
    et al.
    Fikse, Freddy
    Franzén, Jessica
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Strandberg, Erling
    Christensen, O. F.
    De Koning, Dirk-Jan
    Genetic Evaluation of Getting and Recovering from an Intramammary Infection through Longitudinal Models of Somatic Cell Count2013Conference paper (Refereed)
  • 382. Welsh, Alan H.
    et al.
    Hedlin, Dan
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Šova, Markus G.
    The Stabilisation of Model Parameter Estimates from Repeated Surveys with Rare Observations2013In: Australian & New Zeeland Journal of Statistics, ISSN 1467-842X, Vol. 55, no 4, p. 471-491Article in journal (Refereed)
    Abstract [en]

    In many surveys, the domains of study are small and the samples that carry information on a domain can be very small indeed. If the survey is conducted repeatedly there is often a high degree of overlap in samples over time. We show how to use the richness of information over time to compensate for the paucity of cross-sectional information. We propose a model-based estimator of the population total based on stabilised parameter estimates that combine information from different survey periods that are adjacent in time.  The motivating example for this research has been the ProdCom survey as implemented in the UK.

  • 383.
    Wiese, Linda
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Stratification, Sampling and Estimation: Finding the best design for the Swedish Investment Survey2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis, different methods are used to investigate the best design for the Swedish Investment Survey. The methods used today are stratify on number of employees, Neyman-allocation, STSRS-sampling and HT-estimation. The alternative methods in this thesis are stratify on turnover, -sampling and GREG-estimation. These methods are combined into eight combinations and tested on the enterprises and their investments in the Swedish energy domains. The conclusion is that changing the design to stratify on turnover, -sampling and GREG-estimation will provide a smaller standard deviation in most of the energy domains.

  • 384.
    Wretman, Jan
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Unbiased Nonlinear Estimators of a Finite Population Total: Do They Exist?2007In: Statistics in Transition: New Series, ISSN 1234-7655, Vol. 8, no 3Article in journal (Refereed)
    Abstract [en]

    Unbiased nonlinear estimators of a finite population total exist if and only if the sampling design is a nonunicluster design with strictly positive inclusion probabilities.

  • 385.
    Wänström, Linda
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Intelligence and models for cognitive development2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation focuses on cognitive development. In papers I and II, I study a special model, the second order latent growth curve model, that can be used to study cognitive development. Algebraic expressions for the variance of the estimation of slope differences are given. They may be used to calculate the sample sizes needed to detect slope differences between groups. Illustrations of the formulas indicate that sample sizes decrease with effect size, number of indicators and their reliabilities, frequency of observation and duration of the study. In addition, observations near the beginning and end are more important than observations in the middle, and needed sample sizes increase with attrition. Smaller sample sizes are also needed in studies in which baseline levels between groups may be assumed equal, and correlations between factors can either increase or decrease needed sample size.

    Papers III and IV address different aspects of cognitive development. The Flynn effect refers to the observed fact that IQ scores increase over time. In Paper III, we suggest outlining the boundaries within which this effect occurs prior to investigating possible causes. We observe an effect in a test in a large American dataset. This dataset contains information that can be used to outline these boundaries as well as to search for possible causes. Paper IV addresses the observed correlation between sibship size or birth order and cognitive ability. If sibship size negatively affects cognitive ability in children, this should be detected studying children’s cognitive development prior to, and after, the birth of a sibling. Using longitudinal multilevel analyses on a large sample of American children from ages five to fourteen, differences between children of different sibship sizes are noted. Their cognitive abilities do not change following the birth of a sibling however.

  • 386.
    Wänström, Linda
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Sample sizes for two-group second order latent growth curve models2009In: Multivariate Behavioral Research, ISSN 0027-3171, E-ISSN 1532-7906, Vol. 44, no 5, p. 1532-7906Article in journal (Refereed)
    Abstract [en]

    Second-order latent growth curve models (S. C. Duncan & Duncan, 1996; McArdle, 1988) can be used to study group differences in change in latent constructs. We give exact formulas for the covariance matrix of the parameter estimates and an algebraic expression for the estimation of slope differences. Formulas for calculations of the required sample size are presented, illustrated, and discussed. They are checked by Monte Carlo simulations in Mplus and also by Satorra and Saris's (1985) power approximation techniques for small and medium effect sizes (Cohen, 1988). Results are similar across methods. Not surprisingly, sample sizes decrease with effect sizes, indicator reliabilities, number of indicators, frequency of observation, and duration of study. The relative importance of these factors is also discussed, alone and in combination. The use of the sample size formula is illustrated using a modification of empirical results from Stoel, Peetsma, and Roeleveld (2003).

  • 387.
    Wänström, Linda
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Sibship size and cognitive ability: Are cognitive abilities in children affected by the birth of a sibling?Manuscript (Other academic)
  • 388.
    Wänström, Linda
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Slope differences in latent growth curve models under general measurement schemesManuscript (Other academic)
  • 389.
    Wänström, Linda
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Fackle-Fornius, Ellinor
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Minimax optimality and the trinomial spike model2011Report (Other academic)
  • 390. Zhou, Hong-Wei
    et al.
    Zhou, Fang
    Stockholm University, Faculty of Social Sciences, Department of Statistics. Capital University of Economics and Business, China.
    A Meta-analysis on the clinical efficacy and safety of optic capture in pediatric cataract surgery2016In: International Journal of Ophthalmology, ISSN 2222-3959, Vol. 9, no 4, p. 590-596Article in journal (Refereed)
    Abstract [en]

    AIM: To evaluate the clinical efficacy and safety of optic capture in pediatric cataract surgery. METHODS: Searches of peer-reviewed literature were conducted in PubMed, Embase and the Cochrane Library. The search terms were optic capture and cataract. The retrieval period ended in December 2014. Relevant randomized controlled trials (RCTs), case - control studies and cohort studies were included. Meta-analyses were performed. Pooled weighted mean differences and risk ratios with 95% confidence intervals were estimated. RESULTS: Ten studies involving 282 eyes were included, 5 of which were RCTs involving 194 eyes. The application of optic capture significantly reduced both opacification of the visual axis (RR: 0.12; 95% CI: 0.02 to 0.85; P=0.03) and occurrence of geometric decentration (RR: 0.09; 95% CI: 0.02 to 0.46; P=0.004). But it did not significantly affect best corrected visual acuity (BCVA) (WMD: -0.01; 95% CI: -0.07 to 0.05; P =0.75) and influence the occurrence of posterior synechia (RR: 1.53; 95% CI: 0.84 to 2.77; P=0.17). Deposits in the anterior intraocular lens were significantly increased in the optic capture group early after surgery (RR: 1.40; 95% CI: 1.05 to 1.86; P =0.02) and at the last follow-up (RR: 2.30; 95% CI: 1.08 to 4.92; P=0.03). The quality of the evidence was assessed as high. CONCLUSION: The application of optic capture significantly reduces opacification of visual axis and occurrence of geometric decentration but do not significantly improve BCVA with notable safety.

  • 391. Zhou, Hongwei
    et al.
    Zhu, Chongyan
    Xu, Wenya
    Zhou, Fang
    Stockholm University, Faculty of Social Sciences, Department of Statistics. Capital University of Economics and Business, China.
    The efficacy of accommodative versus monofocal intraocular lenses for cataract patients A systematic review and meta-analysis2018In: Medicine (Baltimore, Md.), ISSN 0025-7974, E-ISSN 1536-5964, Vol. 97, no 40, article id e12693Article, review/survey (Refereed)
    Abstract [en]

    Introduction: We performed a systematic review and meta-analysis to evaluate whether accommodative intraocular lenses (AC-IOLs) are superior for cataract patients compared with monofocal IOLs (MF-IOLs). Methods: Pubmed, Embase, Cochrane library, CNKI, and Wanfang databases were searched through in August 2018 for AC-IOLs versus MF-IOLs in cataract patients. Studies were pooled under either fixed-effects model or random-effects model to calculate the relative risk (RR), weighted mean difference (WMD), or standard mean difference (SMD) and their corresponding 95% confidence interval (CI). Distance-corrected near visual acuity (DCNVA) was chosen as the primary outcome. The secondary outcomes were corrected distant visual acuity (CDVA), pilocarpine-induced IOL shift, contrast sensitivity, and spectacle independence. Results: Seventeen studies, involving a total of 1764 eyes, were included. Our results revealed that AC-IOLs improved DCNVA (SMD=-1.84,95% CI=-2.56 to -1.11) and were associated with significantly greater anterior lens shift than MF-IOLs (WMD=-0.30, 95% CI=-0.37 to -0.23). Furthermore, spectacle independence was significantly better with AC-IOLs than with MF-IOLs (RR=3.07, 95% CI=1.06-8.89). However, there was no significant difference in CDVA and contrast sensitivity between the 2 groups. Conclusion: Our study confirmed that AC-IOLs can provide cataract patients with DCNVA and result in more high levels of spectacle independence than MF-IOLs. Further studies with larger data set and well-designed models are required to validate our findings.

  • 392.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Book review 2008In: International Journal of Forecasting, ISSN 0169-2070, Vol. 24, no 1, p. 179-183Article in journal (Refereed)
  • 393.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Det behöver inte går sämre snart för att det går bra nu2007In: Forum för ekonomi och teknik, ISSN 0533-070X, no 7-8, p. 33Article in journal (Refereed)
  • 394.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Det bästa system vi känner till2008In: Forum för ekomomi och teknik, ISSN 0533-070X, no 10, p. 43Article in journal (Refereed)
  • 395.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Efterfrågan på arbetskraft håller konjunkturen uppe2007In: Forum för ekonomi och teknik, ISSN 0533-070X, no 4, p. 32Article in journal (Refereed)
  • 396.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Hur görs prognoser?2007In: Forum för ekonomi och teknik, ISSN 0533-070X, no 11, p. 40Article in journal (Refereed)
  • 397.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Inflation dyrt pris för tillväxt2008In: Forum öfr ekonomi och teknik, ISSN 0533-070X, no 7-8, p. 46Article in journal (Refereed)
  • 398.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Jakten på syndabockar2009In: Forum för ekonomi och teknik, Vol. 5, p. 30-30Article, book review (Other (popular science, discussion, etc.))
  • 399.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Likheter finns i historien2008In: Forum för ekonomi och teknik, ISSN 0533-070X, no 4, p. 39Article in journal (Refereed)
  • 400.
    Öller, Lars-Erik
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Lita inte blint på prognoser2008In: Forum för Ekonomi och teknik, ISSN 0533-070X, no 1, p. 28Article in journal (Refereed)
56789 351 - 400 of 402
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf