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Visar resultat 1 - 5 av 9 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Some Aspects on Confirmatory Factor Analysis of Ordinal Variables and Generating Non-normal Data

    Författare :Hao Luo; Fan Yang-Wallentin; Johan Lyhagen; Karl Jöreskog; Marie Wiberg; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; confirmatory factor analysis; ordinal variables; maximum likelihood; weighted least squares; polychoric correlation; non-normal data; Fleishman s method; Monte Carlo simulation; Statistics; Statistik; Statistics; Statistik;

    Sammanfattning : This thesis, which consists of five papers, is concerned with various aspects of confirmatory factor analysis (CFA) of ordinal variables and the generation of non-normal data. The first paper studies the performances of different estimation methods used in CFA when ordinal data are encountered. LÄS MER

  3. 2. Some Contributions to Description and Validation of the Extreme Value Distribution

    Författare :MirNabi PirouziFard; Statistiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; weighted least squares estimator.; probability plot; power of tests; extreme value distribution; variances and covariances; goodness-of-fit tests; order statistics; Approximations of means;

    Sammanfattning : This thesis focuses on the validation and description of the Gumbel distribution. Since this is a scale and location parameter distribution, the generalized least squares regression of the order statistics on the expected values can be used, without the necessity of iteration, to obtain the best linear unbiased estimates of the parameters. LÄS MER

  4. 3. Adaptive finite element methods for parameter estimation problems in partial differential equations

    Författare :Tao Feng; Mittuniversitetet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; parameter estimation; ¯nite element approximation; adaptive ¯nite element methods; a posteriori error estimates; least squares.; MATHEMATICS; MATEMATIK;

    Sammanfattning : Physical and chemical phenomena are often described by a system of partial di®erential equations. These equations usually involve unknown parameters, which cannot be measured directly but which can be adjusted to make the model predictions match the observed data. LÄS MER

  5. 4. Composite Likelihood Estimation for Latent Variable Models with Ordinal and Continuous, or Ranking Variables

    Författare :Myrsini Katsikatsou; Fan Yang-Wallentin; Irini Moustaki; Karl Gustav Jöreskog; Ruggero Bellio; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; latent variable models; factor analysis; structural equation models; Thurstonian model; item response theory; composite likelihood estimation; pairwise likelihood estimation; maximum likelihood; weighted least squares; ordinal variables; ranking variables; lavaan; Statistics; Statistik;

    Sammanfattning : The estimation of latent variable models with ordinal and continuous, or ranking variables is the research focus of this thesis. The existing estimation methods are discussed and a composite likelihood approach is developed. LÄS MER

  7. 5. Estimation and Inference for Quantile Regression of Longitudinal Data : With Applications in Biostatistics

    Författare :Andreas Karlsson; Johan Lyhagen; Ulf Olsson; Kenneth Carling; Uppsala universitet; []
    Nyckelord :Statistics; Bias correction; Bootstrap; Dependent errors; Hypothesis testing; Nonlinear model; Simulation study; Statistik;

    Sammanfattning : This thesis consists of four papers dealing with estimation and inference for quantile regression of longitudinal data, with an emphasis on nonlinear models.The first paper extends the idea of quantile regression estimation from the case of cross-sectional data with independent errors to the case of linear or nonlinear longitudinal data with dependent errors, using a weighted estimator. LÄS MER