Sökning: "Statistik"

Visar resultat 1 - 5 av 1053 avhandlingar innehållade ordet Statistik.

  1. 1. Contributions to the Theory of Measures of Association for Ordinal Variables

    Författare :Joakim Ekström; Rolf Larsson; Albert Satorra; Uppsala universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Statistics; Statistik; Statistics; statistik;

    Sammanfattning : In this thesis, we consider measures of association for ordinal variables from a theoretical perspective. In particular, we study the phi-coefficient, the tetrachoric correlation coefficient and the polychoric correlation coefficient. LÄS MER

  2. 2. Nonparametric tests for comparing two treatments by using ordinal data

    Författare :Helen Wahlström; Elisabeth Svensson; Jan Lanke; Sture Holm; Örebro universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Statistik; change; clinical trial; Monte Carlo; ordered categorical data; paired data; permutation test; Pitman efficiency; power; stratification; ties; visual analogue scale; Wilcoxon-Mann-Whitney statistic; statistik; Statistics; Statistik; Statistics; Statistik;

    Sammanfattning : This thesis concerns four nonparametric tests for comparing two treatments in a randomized controlled clinical trial when the main response variable generates discrete or continuous ordinal data and measurements are made at baseline and follow-up. In the Wilcoxon-Mann-Whitney test (WMW) the baseline values are not taken into account at all, but in the other three tests both baseline and follow-up values are used. LÄS MER

  3. 3. Optimal Design and Inference for Correlated Bernoulli Variables using a Simplified Cox Model

    Författare :Daniel Bruce; Hans Nyquist; Werner G. Müller; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Cox binary model; correlated binary data; log-odds ratio; D-optimality; E-optimality; power maximization; efficiency; Statistics; Statistik; statistik; Statistics;

    Sammanfattning : This thesis proposes a simplification of the model for dependent Bernoulli variables presented in Cox and Snell (1989). The simplified model, referred to as the simplified Cox model, is developed for identically distributed and dependent Bernoulli variables. LÄS MER

  4. 4. Observed score equating with covariates

    Författare :Kenny Bränberg; Marie Wiberg; Xavier de Luna; Dag Sörbom; Umeå universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Equating; observed score equating; true scores; item response theory; linear equating function; equipercentile equating; kernel equating; covariates; linear regression; mean squared error; Statistics; Statistik; Statistics; statistik;

    Sammanfattning : In test score equating the focus is on the problem of finding the relationship between the scales of different test forms. This can be done only if data are collected in such a way that the effect of differences in ability between groups taking different test forms can be separated from the effect of differences in test form difficulty. LÄS MER

  5. 5. On Bayesian graphical model determination

    Författare :Jukka Corander; Carlo Berzuini; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Bayesian inference; Entropy; Exponential models; Graphical models; Logarithmic utility; Statistics; Statistik; statistik; Statistics;

    Sammanfattning : A graphical model specifies a graph representation of the independence structure of a multivariate distribution, where nodes represent variables and edges association between variables.This thesis introduces methodology for determination of graphical models for multivariate distributions within the exponential family. LÄS MER