Sökning: "image statistics"

Visar resultat 16 - 20 av 417 avhandlingar innehållade orden image statistics.

  1. 16. Test Design for Mean Ability Growth and Optimal Item Calibration for Achievement Tests

    Författare :Jonas Bjermo; Frank Miller; Marie Wiberg; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; test design; item response theory; optimal experimental design; SweSAT; item calibration; vertical scaling; ability growth; computerized adaptive tests; Statistics; statistik;

    Sammanfattning : In this thesis, we examine two topics in the area of educational measurement. The first topic studies how to best design two achievement tests with common items such that a population mean-ability growth is measured as precisely as possible. The second examines how to calibrate newly developed test items optimally. LÄS MER

  3. 17. Essays on Sample Surveys : Design and Estimation

    Författare :Edgar Bueno; Per Gösta Andersson; Maria Giovanna Ranalli; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; GREG estimator; mixture distribution; probability proportional to size sampling; sampling algorithms; sampling design; sampling strategy; survey sampling; stratified sampling; Statistics; statistik;

    Sammanfattning : Sampling is a core stage in every survey. A sampling design carefully elaborated may imply not only a more accurate estimation of the parameters of interest, but also a reduction in the required sample size in a study. In this thesis we consider two particular but connected subjects. LÄS MER

  4. 18. On Estimation and Prediction in Linear Mixed Models : A new approach to studying equal BLUEs and BLUPs

    Författare :Azadeh Chizarifard; Tatjana von Rosen; Katarzyna Filipiak; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Best linear unbiased estimator; Best linear unbiased predictor; Linear zero function; Matrix equations; statistik; Statistics;

    Sammanfattning : Linear mixed models (LMMs) are widely used to analyze repeated, longitudinal, or clustered data in many disciplines, such as biology, medicine, psychology, sociology, economics, etc. One of the essential components of a linear mixed model is its covariance structure, i.e. LÄS MER

  5. 19. Methods for longitudinal brain imaging studies with dropout

    Författare :Tetiana Gorbach; Xavier de Luna; Anders Lundquist; Martin A. Lindquist; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Missing data; nonignorable dropout; sensitivity analysis; uncertainty intervals; pattern-mixture models; aging; cognition; MRI; brain structure; resting-state functional connectivity; Statistics; statistik;

    Sammanfattning : One of the challenges in aging research is to understand the brain mechanisms that underlie cognitive development in older adults. Such aging processes are investigated in longitudinal studies, where the within-individual changes over time are observed. However, several methodological issues exist in longitudinal analyses. LÄS MER

  7. 20. Some Contributions to Heteroscedastic Time Series Analysis and Computational Aspects of Bayesian VARs

    Författare :Oskar Gustafsson; Pär Stockhammar; Domenico Giannone; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Time series; heteroscedasticity; variance stabilizing filters; Bayesian vector autoregressions; Bayesian optimization; variational inference; Statistics; statistik;

    Sammanfattning : Time-dependent volatility clustering (or heteroscedasticity) in macroeconomic and financial time series has been analyzed for more than half a century. The inefficiencies it causes in various inference procedures are well known and understood. Despite this, heteroscedasticity is surprisingly often neglected in practical work. LÄS MER