Search for dissertations about: "Variance components"

Showing result 1 - 5 of 90 swedish dissertations containing the words Variance components.

2. 1. Latent variable models for longitudinal twin data

   Author : Annica Dominicus; Juni Palmgren; Nancy L. Pedersen; Michael G. Kenward; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Latent variable models; twin models; variance components; change point models; non-ignorable nonresponse; likelihood ratio tests; Mathematical statistics; Matematisk statistik;

   Abstract : Longitudinal twin data provide important information for exploring sources of variation in human traits. In statistical models for twin data, unobserved genetic and environmental factors influencing the trait are represented by latent variables. In this way, trait variation can be decomposed into genetic and environmental components. READ MORE

4. 2. Efficient strategies for collecting posture data using observation and direct measurement

   Author : Per Liv; Svend Erik Mathiassen; Marina Heiden; Leif Nilsson; Ingvar Bergdahl; Stephen Bao; Umeå universitet; []
   Keywords : MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Exposure assessment; arm elevation; exposure variability; variance components; random effects model; precision; bias; sample size; sample allocation; calibration; bootstrapping; Occupational and Environmental Medicine; arbets- och miljömedicin;

   Abstract : Relationships between occupational physical exposures and risks of contracting musculoskeletal disorders are still not well understood; exposure-response relationships are scarce in the musculoskeletal epidemiology literature, and many epidemiological studies, including intervention studies, fail to reach conclusive results. Insufficient exposure assessment has been pointed out as a possible explanation for this deficiency. READ MORE

5. 3. Statistical Properties of Preliminary Test Estimators

   Author : Nicklas Korsell; Rolf Larsson; Johan Lyhagen; Tore Schweder; Uppsala universitet; []
   Keywords : Statistics; Linear regression; Preliminary test; Model selection; Test for homoscedasticity; Variance components; Truncated estimators; Inertia of matrices; Statistik;

   Abstract : This thesis investigates the statistical properties of preliminary test estimators of linear models with normally distributed errors. Specifically, we derive exact expressions for the mean, variance and quadratic risk (i.e. the Mean Square Error) of estimators whose form are determined by the outcome of a statistical test. READ MORE

6. 4. Numerical Algorithms for Optimization Problems in Genetical Analysis

   Author : Kateryna Mishchenko; Sverker Holmgren; Dmitrii Silvestrov; Lars Rönnegård; Ann-Charlotte Berglund Sonnhammer; Mälardalens högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Quantitative Trait Loci QTL ; restricted maximum likelihood REML ; variance components; average information AI matrix; Local optimization; Quasi-Newton method; Active Set method; Hessian approximation; BFGS update; Applied mathematics; Tillämpad matematik; Matematik tillämpad matematik;

   Abstract : The focus of this thesis is on numerical algorithms for efficient solution of QTL analysis problem in genetics.Firstly, we consider QTL mapping problems where a standard least-squares model is used for computing the model fit. READ MORE

7. 5. Understanding therapeutic traditions in a multilevel framework - new methodological approaches

   Author : Henrik Ohlsson; Malmö Institutionen för kliniska vetenskaper; []
   Keywords : MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; adherence to guidelines; practice variation; Multilevel models; variance components; determinants of prescription;

   Abstract : Background: The observation of differences in the way apparently similar patients are treated from one health care setting to another, i.e., practice variation, have been recognized in numerous studies. The variations across the health care settings have been shown to exist for different outcomes. READ MORE