Ändra sökning
Avgränsa sökresultatet
123 1 - 50 av 106
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1. Sallnäs Pysander, Eva-Lotta
    et al.
    Mårtensson, Fredrika
    Waern, Annika
    Litsmark, Anna
    Hedblom, Marcus
    Raustorp, Anders
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Zhu, Hui
    Nature and digitalisation challenging the traditional playground2024Ingår i: Urban Forestry & Urban Greening, ISSN 1618-8667, E-ISSN 1610-8167, Vol. 93, s. 1-18, artikel-id 128148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Playing outdoors in nature with peers has been attributed most importance forchildren's healthy development but is increasingly marginalised because of the attractiveness of screen-based play. Careful merging of digital technology into outdoor play environments rich on elements from nature could potentially help bridge digital play with more traditional play activities outdoors. A systematic comparison was made of outdoor play in more or less green settings, with and without digital installations or traditional play equipment. The separate and combined role of digital artefacts, play equipment and natural elements, were investigated, with particular focus on the effects of merging digital materials into nature. A group of children aged 6-8 were involved in a field study in a three-week period playing in a traditional playground, a forest and in a forest with digitally enhanced play artefacts. Children's play behaviour was evaluated using a behavioural tracking method, a questionnaire and a contextual interview with the children, and a physical activity measure, in combination with inventories including maps to document the design, and the ecological and physical status of the settings. The study documents differences in children's play behaviour across the three settings. It differs most between the digital forest setting and the forest setting regarding the play categories imaginative play, physical play and rule play and the digital forest setting stands out when it comes to expressive play and imaginative play. It is discussed how particular attributes in the physical environment influence the overall play flow and the interactive effects of natural material and digital material. Ecologically, the forest and the forest with digitally enhanced artefacts were more diverse than the traditional playground, but the natural material present was important for play in all settings.

  • 2.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Larsson, Rolf
    Adjustment of Anticipatory Covariates in Retrospective Surveys: An Expected Likelihood Approach2023Ingår i: Stats, ISSN 2571-905X, Vol. 6, nr 4, s. 1179-1197Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We address an inference issue where the value of a covariate is measured at the date of the survey but is used to explain behavior that has occurred long before the survey. This causes bias because the value of the covariate does not follow the temporal order of events. We propose an expected likelihood approach to adjust for such bias and illustrate it with data on the effects of educational level achieved by the time of marriage on risks of divorce. For individuals with anticipatory educational level (whose reported educational level was completed after marriage), conditional probabilities of having attained the reported level before marriage are computed. These are then used as weights in the expected likelihood to obtain adjusted estimates of relative risks. For our illustrative data set, the adjusted estimates of relative risks of divorce did not differ significantly from those obtained from anticipatory analysis that ignores the temporal order of events. Our results are slightly different from those in two other studies that analyzed the same data set in a Bayesian framework, though the studies are not fully comparable to each other.

  • 3.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Bayesian Change Point Analysis of Levels and Trends in Total Fertility Rates in Africa, 1960–20202023Ingår i: / [ed] Population Association of America, 2023Konferensbidrag (Refereegranskat)
  • 4.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Fenialdi, Elena
    Bayesian Piecewise Exponential Modeling of Environmental Recidivism in Sweden2023Ingår i: / [ed] Population Association of America, 2023Konferensbidrag (Övrigt vetenskapligt)
  • 5. Holle, Hannah
    et al.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Drees, Randi
    Evaluation of the normal gastrointestinal tract in cats using dual-phase computed tomography2023Ingår i: Journal of Small Animal Practice, ISSN 0022-4510, E-ISSN 1748-5827, Vol. 64, nr 7, s. 463-476Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: In cats, although ultrasonography remains the preferred modality to evaluate the gastrointestinal tract, computed tomographic (CT) examination of the abdomen is commonly performed. However, a normal description of the gastrointestinal tract is lacking. This study describes the conspicuity and contrast enhancement pattern of the normal gastrointestinal tract in cats using dual-phase CT.

    Materials and Methods: Pre- and dual-phase postcontrast (early scan at 30 seconds and late scan mean at 84 seconds) abdominal CT exams of 39 cats without history, clinical signs or diagnosis of gastrointestinal disease were reviewed. The gastrointestinal tract was examined for conspicuity and enhancement pattern using commercially available viewing software (Osirix, v.6.5.2), and diameters of 16 gastrointestinal segments were recorded and compared with published radiographic and ultrasonographic reference values.

    Results: Of the 624 gastrointestinal segments, 530 (84.9%) were identified on precontrast studies and 545 (87.3%) segments on postcontrast studies. Of the gastrointestinal wall segments, 257 (41.2%) were identified on precontrast studies and 314 (50.3%) on postcontrast studies. Gastrointestinal segment diameters correlated well with published normal values, whereas wall thickness measurements usually were smaller compared with sonographic normal values. Early mucosal surface enhancement was frequently seen in the gastric cardia and fundus and ileocolic junction, and a mainly transmural wall enhancement in other gastrointestinal segments.

    Clinical Significance: Dual-phase CT allows for the identification of gastrointestinal tract segments and walls in cats. Contrast enhancement improves conspicuity and demonstrates wall layering in the cardia, fundus and ileocolic junction.

  • 6.
    Quiroz, Matias
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen. ARC Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS), Australia.
    Nott, David J.
    Kohn, Robert
    Gaussian Variational Approximations for High-dimensional State Space Models2023Ingår i: Bayesian Analysis, ISSN 1936-0975, E-ISSN 1931-6690, Vol. 18, nr 3, s. 989-1016Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider a Gaussian variational approximation of the posterior density in high-dimensional state space models. The number of parameters in the covariance matrix of the variational approximation grows as the square of the number of model parameters, so it is necessary to find simple yet effective parametrisations of the covariance structure when the number of model parame-ters is large. We approximate the joint posterior density of the state vectors by a dynamic factor model, having Markovian time dependence and a factor covariance structure for the states. This gives a reduced description of the dependence struc-ture for the states, as well as a temporal conditional independence structure sim-ilar to that in the true posterior. We illustrate the methodology on two examples. The first is a spatio-temporal model for the spread of the Eurasian collared-dove across North America. Our approach compares favorably to a recently proposed ensemble Kalman filter method for approximate inference in high-dimensional hi-erarchical spatio-temporal models. Our second example is a Wishart-based multi-variate stochastic volatility model for financial returns, which is outside the class of models the ensemble Kalman filter method can handle.

  • 7. Liang, Yuli
    et al.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Bayesian Survival Analysis with the Extended Generalized Gamma Model: Application to Demographic and Health Survey Data2022Ingår i: Modern Biostatistical Methods for Evidence-Based Global Health Research / [ed] Ding-Geng Chen; Samuel Manda; Tobias Chirwa, Springer Nature Switzerland AG , 2022, s. 287-318Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    We extend the existing family of flexible survival models by assembling models scattered across the literature into a more knit form and under the same umbrella. New special cases are obtained not only by constraining the shape and scale parameters of the extended generalized gamma (EGG) model to fixed constants, but also by imposing relationships (such as equality, reciprocal, and negative reciprocal) between them. Apart from common parametric distributions such as exponential, Weibull, gamma, and log normal, the further extended family includes Rayleigh, inverse Rayleigh, ammag, inverse ammag, and half-normal distributions. The models are applied, in a Bayesian framework, on time to entry into first marriage among Eritrean men and women based on data from the 2010 Population and Health Survey. The application demonstrates that the further extended family of distributions provides a wide range of alternatives for a baseline distribution in the analysis of survival data. The empirical results reveal that the inverse gamma model fits best the data for men. It also performs closely as good as the EGG model in the data for women as well as in the combined sample.

  • 8.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen. Uppsala University, Uppsala, Sweden.
    Developing an Empirical Demographic Typology of African Countries at the Turn of the Century: The Use of Principal Components-, Cluster- and Discriminant Analyses2022Ingår i: Eritrean Studies Journal, Vol. 1, nr 1, s. 49-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using a combination of multivariate techniques, this paper attemptsto build a classification for 53 African countries with respect to their demographic profiles. Principal Components Analys is applied on 13 demographic indicators allowed for a choice of 3 Principal Components which accounted for 84% of the total variation in the original indicators. The first principal component that accounted for 53% of the variation in the original variables is acontrast between fertility, mortality, and proportion of young peopleon the one hand, and life expectancy and proportion of older people on the other. The second component, accounting for 23%of the variation, is reflection of the actual (1998) and forecasted (2025 and 2050) population sizes. The third component, accounting for 8% of the variation, is basically the population density.

    Cluster Analysis was then applied on these three Principal Components with a view of constructing a classification of the countries. The empirical results reveal that the countries in Northern Africa make their own cluster and that only two countries from the other part of Africa fall in this cluster of North African countries. Further, the three most populated countries of Sub-Saharan Africa make their own cluster. Else, the results show no unique spatial mix of the other countries. A separate discriminant analysis, on the other hand, classifies the seven North African countriesin one cluster (100 % correct classification). Among the 16 countries in West Africa 69 % were classified correctly while the corresponding figures of correct classification for East, Central and Southern Africa were 65 %, 63 % and 60 %, respectively. Thus, the results support a classification of Africa into North Africa and the rest (Sub-Saharan Africa) with respect to demographic profiles. However, any attempt to classify countries in the rest (Sub-Saharan) Africa with respect to their demographicbe havior should be based on other (such as socioeconomic, political, etc.) indicators rather than on spatial classification. A deeper investigation on similarities of the countries that fall in respective clusters and a follow-up of the study with more recent data could be areas worth investigating in the future.

  • 9.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Diagonal Reference Modelling of the Effects of Educational Differences between Couples on Womens’ Health-Care Utilization in Eritrea2022Ingår i: Modern Biostatistical Methods for Evidence-Based Global Health Research / [ed] Ding-Geng Chen; Samuel Manda; Tobias Chirwa, Cham: Springer Nature Switzerland AG , 2022, s. 9-20Kapitel i bok, del av antologi (Refereegranskat)
  • 10.
    Munezero, Parfait
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Dynamic Bayesian adjustment of anticipatory covariates in retrospective data: application to the effect of education on divorce risk2022Ingår i: Journal of Applied Statistics, ISSN 0266-4763, E-ISSN 1360-0532, Vol. 49, nr 6, s. 1382-1401Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We address a problem in inference from retrospective studies where the value of a variable is measured at the date of the survey but is used as covariate to events that have occurred long before the survey. This causes problem because the value of the current-date (anticipatory) covariate does not follow the temporal order of events. We propose a dynamic Bayesian approach for modelling jointly the anticipatory covariate and the event of interest, and allowing the effects of the anticipatory covariate to vary over time. The issues are illustrated with data on the effects of education attained by the survey-time on divorce risks among Swedish men. The overall results show that failure to adjust for the anticipatory nature of education leads to elevated relative risks of divorce across educational levels. The results are partially in accordance with previous findings based on analyses of the same data set. More importantly, our findings provide new insights in that the bias due to anticipatory covariates varies over marriage duration.

  • 11.
    Munezero, Parfait
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Dynamic Bayesian Modelling of Educational and Residential Differences in Family Initiation among Eritrean Men and Women2022Ingår i: Modern Biostatistical Methods for Evidence-Based Global Health Research / [ed] Ding-Geng Chen; Samuel Manda; Tobias Chirwa, Springer Nature Switzerland AG , 2022, s. 319-337Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    We propose a dynamic Bayesian survival model for analyzing differentials in the timing of family initiation. Such formulation relaxes the strong assumption of constant hazard ratio in conventional proportional hazards models and allows covariate effects to vary over time. Inference is fully Bayesian, and efficient sequential Monte Carlo (particle filter) is used to sample from the posterior distribution. We illustrate the proposed model with data on entry into first marriage among Eritrean men and women surveyed in the 2010 Eritrean Population and Health Survey. Results from the conventional proportional hazards model indicate significant differences in family initiation among all educational and residential groups. In the dynamic model, on the other hand, only one educational and one residential group among the women and only one residential group among the men differ from their respective baseline groups. Since the empirical relative intensities of entry into first marriage vary across respondents’ ages, we argue that the proposed dynamic model captures differentials in family initiation more accurately.

  • 12. Liang, Yuli
    et al.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Further Extensions of the Extended Generalized Gamma Model and Their Application to Bayesian Modeling of Family Initiation in Eritrea2022Ingår i: / [ed] Population Association of America, 2022Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Existing family of flexible survival models is further extended by assembling models scattered across the literature under the same umbrella. New special cases areobtained not only by constraining the shape and scale parameters to fixed constants,but also by imposing relationships (like equality, reciprocal, and negative reciprocal) between them. Apart from common parametric distributions like exponential,Weibull, gamma, and log-normal; the further extended family includes Rayleigh, inverse Rayleigh, Ammag, inverse Ammag, and half-normal distributions. The modelsare applied, in a Bayesian framework, on time to entry into first marriage amongEritrean men and women based on data from the 2010 Population and Health Survey.The further extended family of distributions provides a wide range of alternativesfor a baseline distribution in the analysis of survival data. The Inverse gamma modelfits the men-data best while it performs as good as the EGG model in the womenand combined sample.

  • 13.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Peristera, Paraskevi
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Regional Differences in the Effects of Education on Parity Progression Ratios in Ethiopia: A Random Effect Sequential Probit Modeling Approach2022Ingår i: / [ed] Population Association of America, 2022Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Sequential probit approach is used to model differentials in the effects of women’seducation on parity progression in Ethiopia. Since reasons to have a first childmay differ from those to have, say, a second or third child, we allow the effects ofcovariates on the progression propensities to vary between parities in the same model.Data used for illustration come from the Ethiopian Mini Demographic and HealthSurvey of 2019 in which 8885 women from 11 regions were interviewed. Resultsshow that the sequential model provides more insight than conventional modelswhen exploring the association between education and parity progression. We alsofound similarities and differences in the effects of education on parity progressionamong the regions. A random effect term to account for women’s clustering withinhouseholds was significant in a model for the entire country but disappeared whenregion was included as a covariate in the model.

  • 14.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Peristera, Paraskevi
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Sequential Probit Modelling of Regional Differences in the Effects of Education on Parity Progression Ratios in Ethiopia2022Ingår i: Modern Biostatistical Methods for Evidence-Based Global Health Research / [ed] Ding-Geng Chen; Samuel Manda; Tobias Chirwa, Cham: Springer Nature Switzerland AG , 2022, s. 21-40Kapitel i bok, del av antologi (Refereegranskat)
  • 15.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Akinyi Lagehäll, Amanda
    Department of Statistics, Stockholm University, Stockholm, Sweden.
    Yemane, Elelta
    Department of Statistics, Stockholm University, Stockholm, Sweden.
    Stratified Multilevel Modelling of Survival Data: Application to Modelling Regional Differences in Transition to Parenthood in Ethiopia2022Ingår i: Modern Biostatistical Methods for Evidence-Based Global Health Research / [ed] Ding-Geng Chen; Samuel Manda; Tobias Chirwa, Springer Nature Switzerland AG , 2022, s. 431-456Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    This chapter presents a multilevel extension of the Cox proportional hazards model where a shared frailty term is included to account for clustering of women within households. The extended model is used to analyze regional differences in the intensity of transition to parenthood among 15019 Ethiopian women aged 15–49 years old in the country’s Demographic and Health Survey of 2016. Women’s birth cohort, residence and educational level were used as background variables. Conventional Cox proportional hazards models and two multilevel models (with gamma distributed and log-normal distributed frailty terms) are fitted to data for the entire country and, separately, for each of the nine regions and two city administrations. We found that household frailty effects are fairly small in the nine regions but the log-normal frailties were significant in the entire country and the two city administrations which are relatively heterogeneous with inhabitants from many ethnic groups. We also found regional differences in the effects of the background variables on the intensity of transition to parenthood but the effects were generally stable across the three models in each region. Overall, we recommend use of multilevel survival models to account for clustering of women into households and proper care in the choice of distribution of the household random effects.

  • 16.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Akinyi Lagehäll, Amanda
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Yemane, Elelta
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Stratified Shared- and Correlated-Frailty Modeling of Regional Differences in Transition to Parenthood in Ethiopia2022Ingår i: / [ed] Population Association of America, 2022Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Multilevel Cox proportional hazards models with shared- and correlated-frailty termsto account for clustering of women within households is used to analyse regionaldifferences in transition to parenthood among 15019 Ethiopian women from thecountry’s Demographic and Health Survey (DHS) of 2016. We found that bothgamma- and lognormal-distributed shared household frailty effects are fairly smallin the nine regions though the log-normal frailties were significant in the entirecountry and the two city administrations which are relatively heterogeneous withinhabitants from many ethnic groups. Allowing for correlation between the randomeffects within households revealed significant clustering effects in almost all regions.We also found regional differences in the effects of background variables on the intensity of transition to parenthood. Overall, we recommend use of correlated frailtymodels to account for clustering of women into households and proper care in thechoice of distribution of the household random effects.

  • 17.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Disentangling Selection and Causality in Assessing the Efficacy of Health Inputs on Birth Outcome2021Konferensbidrag (Refereegranskat)
  • 18.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Munezero, Parfait
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Bayesian change-point modelling of the effects of 3-points-for-a-win rule in football2020Ingår i: Journal of Applied Statistics, ISSN 0266-4763, E-ISSN 1360-0532, Vol. 47, nr 2, s. 248-264Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine the effects of the 3-points-for-a-win (3pfaw) rule in the football world. Data that form the basis of our analyses come from seven leagues around the world (Albania, Brazil, England, Germany, Poland, Romania, and Scotland) and consist of mean goals and proportions of decided matches over a period of about six years before- and about seven years after the introduction of the rule in the respective leagues. Bayesian change-point analyses and Shiryaev-Roberts tests show that the rule had no effects on the mean goals but, indeed, had increasing effects on the proportions of decided matches in most of the leagues studied. This, in turn, implies that while the rule has given teams the incentive to aim at winning matches, such aim was not achieved by scoring excess goals. Instead, it was achieved by scoring enough goals in order to win and, at the same time, defending enough in order not to lose. Our results are in accordance with recent findings on comparing the values of attack and defense - that, in top-level football, not conceding a goal is more valuable than scoring a single goal.

  • 19. Tongur, Can
    et al.
    Thorburn, Daniel
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Problemet med KPI som enda inflationsmått2020Ingår i: Ekonomisk Debatt, ISSN 0345-2646, nr 2, s. 65-71Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 20.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Herrström, Sofia
    Diagonal Reference Modeling of Effects of Couples' Educational Differences on Women's Health Care Utilisation in Sub-Saharan Africa2019Ingår i: / [ed] Population Association of America, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Studies on associations between education and demographic- orhealth-outcome have traditionally used womanís education (alone orin combination with partnerís education) as regressors in models relating covariates to the outcome. In this study, we adapt modelsdeveloped in the social mobility litearture to examine e§ects of differences between couplesíeducational levels on womenís propensity toutilise facilities (specically deliver in health facilities). Diagonal Reference Modeling (DRM) which accounts for origin (womanís education),destination (partnerís education), and ímobilityí(di§erences betweencouplesíeducational levels) is applied on data from Demographic andHealth Surveys (DHS) in Öve African countries (Angola, Ethiopia,Kenya, Namibia, and Nigeria). The results reveal strong e§ects ofeducational di§erences on womenís decision to deliver at health facilities. More importantly, such strong e§ects would be concealed if datais analyzed using standard modeling approaches. Use of Diagonal Reference Models is strongly recommended if correct policy interventionsare to be implemented.

  • 21.
    Munezero, Parfait
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Dynamic Bayesian Adjustment of Educational Gradients in Divorce Risks: Disentangling Causation and Misclassification2019Ingår i: / [ed] Population Association of America, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    We address a problem in causal inference from retrospective surveys where the value of a covariate is measured at the date of the survey but is used to explain behaviour that has occurred long before the survey. This causes bias because the anticipatory covariate does not follow the temporal order of events. We propose a Bayesian dynamic modelling approach that allows effects of the anticipatory covariate to vary over time and, thereby, restore its value at the event of interest. The issues are illustrated with data on the effects of anticipatory educational level on divorce risks among Swedish men. The overall results show that failure to adjust for the anticipatory nature of education leads to underestimation of the relative risks of divorce across educational levels. The results build, in part, on previous analyses of the same data set but also reveal that the degree of underestimation varies over marriage durations.

  • 22.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Larsson, Rolf
    Maximum Likelihood Adjustment of Anticipatory Covariates in the Analysis of Retrospective Data2019Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A multiplicative hazard model in the presence of anticipatory covariates is estimated by maximum likelihood. The case study concerns the e§ects of educational level on risks of divorce. For individuals with anticipatory educational levels, conditional probabilities of having attained the reported level before marriage are used as weights in the likelihood. The adjusted estimates of relative risks do not di§er signiÖcantly from those from anticipatory analysis.

    Ladda ner fulltext (pdf)
    fulltext
  • 23.
    Billingsley, Sunnee
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Sociologiska institutionen.
    Drefahl, Sven
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Sociologiska institutionen.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    An application of diagonal reference models and time-varying covariates in social mobility research on mortality and fertility2018Ingår i: Social Science Research, ISSN 0049-089X, E-ISSN 1096-0317, Vol. 75, s. 73-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In social mobility research, the diagonal reference model (DRM) is argued to best isolate the effect of social mobility from origin and destination status effects. In demographic research, standard analyses of the duration until an event occurs rely heavily on the appropriate use of covariates that change over time. We apply these best-practice methods to the study of social mobility and demographic outcomes in Sweden using register data that covers the years 1996–2012. The mortality analysis includes 1,024,142 women and 747,532 men and the fertility analysis includes 191,142 women and 164,368 men. We identify the challenges inherent in this combination and present strategies with an application to how social mobility is related to both fertility and mortality. Our application is successful at incorporating all requirements related to these methods. Our findings suggest, however, that certain data characteristics, such as a relatively high share of missing data, can be problematic. We also find that controlling for origin and destination status generally provides acceptable estimates of the mobility association in the specific case of Sweden and the relationship between social mobility and both fertility and mortality.

  • 24.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Munezero, Parfait
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Bayesian Change-point Modelling of the Effects of 3-points-for-a-win Rule in Football2018Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We examine the e⁄ects of the 3-point-for-a-win (3pfaw) rule in the football (soccer) world. Data on mean goals and proportions of decided matches from seven leagues around the world form the basis of our analyses. Bayesian change-point analysis shows that the rule had no e⁄ects on the mean goals in any of the leagues but, indeed, had increasing e⁄ects on the proportions of decided matches in most of the leagues studied. This, in turn, implies that while the rule has given teams the incentive to aim at winning matches, such aim was achieved not by scoring excess goals. Instead, it was achieved by scoring enough goals in order to win and, at the same, defending enough in order not to lose.

  • 25.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Bayesian change-point modelling of the effects of 3-points-for-a-win rule in football2018Ingår i: The 27th Nordic Conferencein Mathematical Statistics Abstracts, 2018, s. 24-24Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    We examine the effects of the 3-point-for-a-win (3pfaw) rule in the football (soccer) world. Dataon mean goals and proportions of decided matches from seven leagues around the world form thebasis of our analyses. Bayesian change-point analysis shows that the rule had no effects on themean goals in any of the leagues but, indeed, had increasing effects on the proportion of decidedmatches in some of the leagues studied. This, in turn, implies that while the rule has given teamsthe incentive to aim at winning games, such aim was not achieved by scoring more goals but byscoring enough in order to win and, at the same, defending enough in order not to lose.

  • 26. Kum, Cletus Kwa
    et al.
    Thorburn, Daniel
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Björkman, Anders
    Gil, José Pedro
    Effects of Some Biological Covariates on the Probability of First Recurrence of Malaria following Treatment with Artemisinin Combination Therapy2018Ingår i: International Journal of Statistics in Medical Research, ISSN 1929-6029, Vol. 7, nr 1, s. 1-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many investigations have shown that artemisinin-based combination therapies are effective in the treatment of uncomplicated malaria and that they do not increase parasite resistance to treatment as much as treatment with single substance. We study the relation between some biological covariates and the time to first recurrence of malaria for children treated for malaria in a clinical trial. One group received artesunate plus sulfadoxine-pyrimethamine and the other only sulfadoxine-pyrimethamine. We consider the event malaria-free for the first 42 (and 84) days. We use logistic regression models for the analyses. The main results show that the probability of no recurrence is higher if the parasite density in the blood is high. The results are inconclusive for other explanatory biological variables. The infecting parasites having genes that indicate resistance, gave different results at the two different treatment centres. There was no appreciable difference in the effects of treatment over the two follow-up periods and these treatments do not have any effect on the probability of a recurrence.

  • 27.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Environmental recidivism in Sweden: distributional shape and effects of sanctions on duration of compliance2018Ingår i: Quality and quantity, ISSN 0033-5177, E-ISSN 1573-7845, Vol. 52, nr 2, s. 21s. 869-882Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The study examines the association between the size of previous environmental sanction charges and subsequent compliance towards environmental regulations. Data used for the study come from about 9000 Swedish firms fined sometime between January 2002 and December 2012. Probabilities of compliance across various levels of sanctions are estimated using life-table methods and tested for equality using standard nonparametric methods. Association between size of sanction charges and subsequent behaviour is modelled by proportional hazard model for the rate of recidivism as well as by a family of flexible parametric accelerated failure-time models for the duration of compliance. The results show that duration of compliance may be described by a log-normal distribution. Further, it is demonstrated that sanctions charges do have significant detering effects on the risk of recidivism though the strength of the detering effect depends on whether or not we account for other possible correlates of recidivism. Possible explanations of the results and their policy implications are discussed; limitations of the current study highlighted; and potential extensions for future studies outlined. 

  • 28.
    Andreev, Andriy
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Morlanes, Jose Igor
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    On Simulation of a Fractional Ornstein-Uhlenbeck Process of the Second Kind by the Circulant Embedding Method2018Ingår i: Stochastic Processes and Applications: SPAS2017, Västerås and Stockholm, Sweden, October 4-6, 2017 / [ed] Sergei Silvestrov, Anatoliy Malyarenko, Milica Rančić, Springer, 2018, s. 155-164Kapitel i bok, del av antologi (Refereegranskat)
  • 29. Riazoshams, Hossein
    et al.
    Midi, Habshah
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Robust Nonlinear Regression: With Application Using R2018Bok (Refereegranskat)
    Abstract [en]

    Robust Nonlinear Regression: with Applications using R develops new methods in robust nonlinear regression and implements a set of objects and functions in S-language, under SPLUS and R software. The software covers a wide range of robust nonlinear fitting and inferences, and is designed to provide facilities for computer users to define their own nonlinear models as an object, and fit models using classic and robust methods as well as detect outliers. The implemented objects and functions can be applied by both practitioners and researchers.

    The main areas that will be covered in the book include theories and application of Nonlinear Robust Regression. In both parts the classic and robust aspects of nonlinear regression will be discussed. Outlier effects is among the main focus in the book.

  • 30.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Statistical Analysis of Educational and Urban-Rural Differences in Marriage-timing: Evidence from the 2010 Eritrean Population and Health Survey for Women and Men2018Ingår i: Proceedings of the International Conference on Eritrean Studies, 20-22 July 2016 / [ed] Zemenfes Tsighe, Saleh Mahmud Idris, Yonas Mesfun Asfaha, Senai Woldeab Andemariam, Rediet Kifle Taddese, Ghebrebrhan Ogubazghi, Asmara: National Higher Education and Research Institute , 2018, 2, s. 1097-1124Kapitel i bok, del av antologi (Refereegranskat)
  • 31.
    Peristera, Paraskevi
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Another Look at the Relationship between Cohabitation and Marriage: The Use of Crude and Net Probabilities2017Ingår i: Bulletin of Sociological Methodology, ISSN 0759-1063, E-ISSN 2070-2779, Vol. 136, s. 66-73Artikel i tidskrift (Refereegranskat)
    Abstract [fr]

    Un nouveau regard sur la relation entre la cohabitation et le mariage - L’utilisation desprobabilite ́s brutes et nettes - La cohabitation informelle est-elle un pre ́lude au mariage ouun remplacement permanent? Dans cet article, nous proposons une approche base ́esurlarelation the ́orique entre les probabilite ́s brutes et nettes de mariage dans un cadre derisque concurrentiel. Les analyses base ́es sur la dynamique familiale chez les hommessue ́dois ne ́s en 1936-1964 montrent que les probabilite ́s du mariage augmentent si lacohabitation a e ́te ́e ́limine ́e (et que les probabilite ́s de cohabitation augmentent si lemariage a e ́te ́e ́limine ́). En outre, les gains dans les probabilite ́s nets augmentent aux aˆgesprincipaux de la formation des familles (20-28) mais sont moins significatifs a`d’autres aˆges.Ces re ́sultats appuient (au moins pour les donne ́es disponibles) l’argument selon lequel lacohabitation informelle sert de pre ́lude au mariage plutoˆt qu’un remplacement permanent.

  • 32.
    Morlanes, José Igor
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Andreev, Andriy
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Simulation of fractional Ornstein-Uhlenbeck of the second kind by Circulant Embedding method2017Konferensbidrag (Övrigt vetenskapligt)
  • 33.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Peristera, Paraskevi
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Another Look at the Relationship Between Cohabitation and Marriage2016Ingår i: Abstract: Session: P2 Marriage, Family, Households, and Unions / [ed] Population Association of America, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Whether informal cohabitation is a prelude to marriage or a permanent replacement to it has been a question of interest for researchers in the past decades. The methdological approaches proposed to answer this question have been based on information on subsequent behaviour of cohabiting couples. In this paper we propose an approach based on the theoretical relationship between crude and net probabilities of marriage in a competing-risk framwork. Analyses based on family dynamics among Swedish men born 1936-1964 show that probabilities of marriage increase if cohabitation was eliminated (and that probabilities of cohabitation increase if marriage was eliminated). Further, the gains in net probablities increase at the prime ages of family formation (20-28) but are less signicant at other ages. Such results support (at least for the data at hand) the argument that informal cohabitation serves as a prelude to marriage rather than a permanent replacement to it.

  • 34.
    Billingsley, Sunnee
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Sociologiska institutionen.
    Drefahl, Sven
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Sociologiska institutionen.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Diagonal Reference Models in Longitudinal Analyses of Fertility and Mortality2016Ingår i: Abstrect: Session: 73 New Demographic Measures and Analytic Approaches / [ed] Population Association of America, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Diagonal reference models (DRM) are considered the only correct method of estimating an effect of social mobility that is distinct from origin and destination status. This method has become standard in analyses of other social phenomena as well. This study considers how diagonal reference models (DRM) may be applied to demographic processes (mortality and fertility) that are analyzed longitudinally and compares findings between a standard demographic approach and the DRM. Overall, the difference we see between the DRM and others is that DRM picks up weakly significant effects we otherwise do not see. This finding indicates that we gain social mobility effects rather than lose them when we use a DRM model, which means the standard demographic approach appears to run the risk of underestimating a mobility effect at worst.

  • 35. Welderufael, B. G.
    et al.
    de Koning, D. J.
    Janss, L. L. G.
    Franzen, Jessica
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Fikse, W. F.
    Simultaneous genetic evaluation of simulated mastitis susceptibility and recovery ability using a bivariate threshold sire model2016Ingår i: Acta agriculturae Scandinavica. Section A, Animal science, ISSN 0906-4702, E-ISSN 1651-1972, Vol. 66, nr 3, s. 125-134Artikel i tidskrift (Refereegranskat)
    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.

  • 36.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Wänström, Linda
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen. Linköping University, Sweden.
    Adjusting for selection bias in assessing the relationship between sibship size and cognitive performance2015Ingår i: Journal of the Royal Statistical Society: Series A (Statistics in Society), ISSN 0964-1998, E-ISSN 1467-985X, Vol. 178, nr 4, s. 22s. 925-944Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Consistent negative correlations between sibship size and cognitive performance (as measured by IQ and other mental aptitude tests) have been observed in past empirical studies. However, the issue of potential selection process in the decision to have larger families (largersibship size) has been partly neglected in past single- and multilevel investigations. The present work extends existing knowledge in three aspects: (1) as factors affecting decision to increase family size may vary across the number and composition of current family size, we propose a sequential probit model (as opposed to binary or ordered models) for the propensity to increase sibship size; (2) we investigate if families who choose to increase family size are a representative random sample of the population of families or there exists selection; (3) in order to disentangle selection and causality we propose a multilevel multiprocess modelling where a continuous model for performance is estimated jointly with a sequential probit model for family-size decisions. The issues are illustrated through analyses of scores on PIAT tests among children of the NLSY79. We found substiantial between-family heterogeneity in the propensity to increase family size - thereby providing empirical evidence in support of the admixture hypothesis. Ignoring such adverse selection led to overestimation of the negative effects of sibship size on cognitive performance but our multiprocess modelling could mitigate the biasing effects of selection.

  • 37.
    Quiroz, Matias
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Bayesian Inference in Large Data Problems2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the last decade or so, there has been a dramatic increase in storage facilities and the possibility of processing huge amounts of data. This has made large high-quality data sets widely accessible for practitioners. This technology innovation seriously challenges traditional modeling and inference methodology.

    This thesis is devoted to developing inference and modeling tools to handle large data sets. Four included papers treat various important aspects of this topic, with a special emphasis on Bayesian inference by scalable Markov Chain Monte Carlo (MCMC) methods.

    In the first paper, we propose a novel mixture-of-experts model for longitudinal data. The model and inference methodology allows for manageable computations with a large number of subjects. The model dramatically improves the out-of-sample predictive density forecasts compared to existing models.

    The second paper aims at developing a scalable MCMC algorithm. Ideas from the survey sampling literature are used to estimate the likelihood on a random subset of data. The likelihood estimate is used within the pseudomarginal MCMC framework and we develop a theoretical framework for such algorithms based on subsets of the data.

    The third paper further develops the ideas introduced in the second paper. We introduce the difference estimator in this framework and modify the methods for estimating the likelihood on a random subset of data. This results in scalable inference for a wider class of models.

    Finally, the fourth paper brings the survey sampling tools for estimating the likelihood developed in the thesis into the delayed acceptance MCMC framework. We compare to an existing approach in the literature and document promising results for our algorithm.

    Ladda ner fulltext (pdf)
    kappa fulltext
    Ladda ner (jpg)
    omslagsframsida
  • 38. Hiswåls, Anne-Sofie
    et al.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Wijk, Katarina
    Öberg, Peter
    Soares, Joaquim
    Macassa, Gloria
    Employment Status and Suicidal Ideation during Economic Recession2015Ingår i: Health science journal, ISSN 1791-809X, Vol. 9, nr 1, s. 1-9, artikel-id 13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     

    Objective: Suicide is a public health problem and an important indicator of severe mental ill-health. Thus, identifying risk factors for suicidal ideation is a public health priority. The aim of this study was to examine the relationship between employment status and suicidal ideation in Gävleborg County.

    Method:

    The study used data from the 2010 Health in Equal Terms survey, a cross-sectional survey carried out in Gävleborg County in Sweden. A total of 4,245 individuals, aged 16–65 years were included in the analyses. Descriptive and logistic regression analyses were carried out to assess the relationship between employment status and suicidal ideation

    Results:

    Individuals outside the labour market had odds of suicidal ideation of 4.21 (CI 3.14-5.64) compared to their employed counterparts. Controlling for other covariates, reduced the risk from 4.21(CI 3.14-5.64) in model I, to 1.73 (CI 1.16- 2.57) in model IV, but remained statistically significant. In addition, other variables were associated with suicidal ideation.

    Conclusion:

    There was a statistically significant association between being out of work and suicidal ideation. The association was explained partly by demographic, socio-economic and self-reported psychological variables. Results of the study suggest the need for primary prevention strategies among those out of the labour market, especially during times of economic hardship.

  • 39.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Peristera, Paraskevi
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Sequential Modeling of Parity Progression in Sub-Saharan Africa2015Ingår i: / [ed] Population Association of America, 2015Konferensbidrag (Refereegranskat)
  • 40.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Elisa, Woldeyesus
    A Family of Flexible Parametric Duration Functions and their Applications to Modeling Child-Spacing in Sub-Saharan Africa2014Ingår i: Advanced techniques for modelling maternal and child health in Africa / [ed] Ngianga-Bakwin Kandala, Gebrenegus Ghilagaber, Springer, 2014, s. 185-209Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Examining the dynamics of child spacing is of interest for several reasons. First, several inferences are consistent with the view that in much of the developing world, women with large families have shorter birth intervals than those with smaller families. There is thus an indication of an inverse relationship between spacing and completed or cumulative fertility. The spacing of births also has a significant bearing on maternal and child health through the dynamics of sibling competition, maternal depletion and interval effect hypotheses.

  • 41.
    Peristera, Paraskevi
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    A Mixture Model for Nuptiality Data with Long-Term Survivors.2014Konferensbidrag (Refereegranskat)
  • 42.
    Ghilagaber, Gebrenegus
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Wänström, Linda
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Adjusting for Selection Bias in Assessing the Relationship Between Sibship Size and Cognitive Performance2014Konferensbidrag (Refereegranskat)
  • 43. Manda, Samuel O. M.
    et al.
    Kandala, Ngianga-Bakwin
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Advanced Techniques for Modelling Maternal and Child Health in Africa2014Ingår i: Advanced Techniques for Modelling Maternal and Child Health in Africa / [ed] Samuel O. M. Manda; Ngianga-Bakwin Kandala; Gebrenegus Ghilagaber, Dordrecht: Springer, 2014, s. 1-7Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    More than ten million women die or experience adverse consequences during pregnancy and childbirth each year (WHO 2005). Furthermore, nearly nine million children under the ages of 5 years die each year, largely from preventable and treatable diseases (UNICEF 2010). The hardest hit countries in poor maternal health (defined as the health of mothers during pregnancy, childbirth, and in the postpartum period) and child health (defined as the health of children from birth through adolescence) are in the developing world. For example, the global estimates of maternal and child mortality rates in 2008 were at 260 per 100,000 and 60 per 1,000 live births, respectively. The rates ranged from 21 to 620 and 13 to 127 respectively, with the African region at the top of both ranges (WHO 2011)

  • 44.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Advances in modelling maternal and child health in Africa: what have we learned and what is next?2014Ingår i: Advanced techniques for modelling maternal and child health in Africa / [ed] Ngianga-Bakwin Kandala; Gebrenegus Ghilagaber, Dordrecht: Springer Netherlands, 2014, s. 321-325Kapitel i bok, del av antologi (Refereegranskat)
  • 45.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Analysis of grouped survival data: a synthesis of various traditions and application to modeling childhood mortality in Eritrea2014Ingår i: Advanced techniques for modelling maternal and child health in Africa / [ed] Ngianga-Bakwin Kandala; Gebrenegus Ghilagaber, Dordrecht: Springer, 2014, s. 107-122Kapitel i bok, del av antologi (Refereegranskat)
  • 46.
    Thorburn, Daniel
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Tongur, Can
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Assessing direct and indirect seasonal decomposition in state space2014Ingår i: Journal of Applied Statistics, ISSN 0266-4763, E-ISSN 1360-0532, Vol. 41, nr 9, s. 2075-2091Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of whether seasonal decomposition should be used prior to or after aggregation of time series is quite old. We tackle the problem by using a state-space representation and the variance/covariance structure of a simplified one-component model. The variances of the estimated components in a two-series system are compared for direct and indirect approaches and also to a multivariate method. The covariance structure between the two time series is important for the relative efficiency. Indirect estimation is always best when the series are independent, but when the series or the measurement errors are negatively correlated, direct estimation may be much better in the above sense. Some covariance structures indicate that direct estimation should be used while others indicate that an indirect approach is more efficient. Signal-to-noise ratios and relative variances are used for inference.

  • 47.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Disentangling selection and causality in assessing the effects of health inputs on child survival: case studies from east Africa2014Ingår i: Advanced Techniques for Modelling Maternal and Child Health in Africa / [ed] Ngianga-Bakwin Kandala, Gebrenegus Ghilagaber, Dordrecht: Springer Netherlands, 2014, s. 11-28Kapitel i bok, del av antologi (Refereegranskat)
  • 48. Hiswåls, Anne-Sofie
    et al.
    Ghilagaber, Gebrenegus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Walander, Anders
    Wijk, Katarina
    Öberg, Peter
    Soares, Joaquim
    Macassa, Gloria
    Employment status and inequalities in self-reported health2014Ingår i: Epidemiology, Biostatistics and Public Health, ISSN 2282-2305, E-ISSN 2282-0930, Vol. 11, nr 4, s. e10006-1-e1006-11Artikel i tidskrift (Refereegranskat)
  • 49. Welderufael, B. G.
    et al.
    de Koning, D. J.
    Janss, L.
    Franzén, Jessica
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Fikse, W. F.
    Longitudinal Analysis of Somatic Cell Count for Joint Genetic Evaluation of Mastitis and Recovery Liability2014Ingår i: Proceedings, 10th World Congress of Genetics Applied to Livestock Production, 2014, artikel-id 095Konferensbidrag (Refereegranskat)
    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.