Sökning: "jackknife"

Visar resultat 1 - 5 av 10 avhandlingar innehållade ordet jackknife.

1. 1. Influences of Statistical Analyses on Result Presentations of Oral Implant Treatment

   Författare :Irene Herrmann; Göteborgs universitet; []
   Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Statistical methods; oral implants; dependence; prognostic risk factors; multivariate analysis; bone-combination; Jackknife; log rank test; variance;

   Sammanfattning : Abstract Evaluation of oral implants involves at least three major components: statistical methods, study design and success criteria. The aims of the current thesis were to investigate how different statistical methods affect the outcome of oral implant treatment and to statistically determine if any dependence among implants placed in the same jaw exists. LÄS MER

3. 2. EM Estimation in Phase Type Models

   Författare :Marita Olsson; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; phase type distributions; coxian distribution; EM algorithm; I-divergence; density estimation; right censoring; interval censoring; standard error estimation; asymptotic theory; jackknife; relapse clinical trials; survival data; hidden Markov chain; I-divergence;

   Sammanfattning : This thesis consists of four articles whose theme in common is the class of phase type distributions. In the first article an EM algorithm is presented to estimate the parameters of a phase type distribution of fixed order. Also, it is shown that the algorithm can be used to approximate other continuous distributions by phase type distributions. LÄS MER

4. 3. Some properties of measures of disagreement and disorder in paired ordinal data

   Författare :Hans Högberg; Elisabeth Svensson; Sture Holm; Örebro universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; agreement; augmented ranks; categorical data; disorder; jackknife; paired ordinal data; rating scales; sample size; sampling distribution; simulation; U-statistics; variance; SOCIAL SCIENCES; SAMHÄLLSVETENSKAP; Statistics; Statistik; Statistics; Statistik;

   Sammanfattning : The measures studied in this thesis were a measure of disorder, D, and a measure of the individual part of the disagreement, the measure of relative rank variance, RV, proposed by Svensson in 1993. The measure of disorder is a useful measure of order consistency in paired assessments of scales with a different number of possible values. LÄS MER

5. 4. Contributions to generalized Wilcoxon rank tests

   Författare :Marie-Louise Öhman; Hans Nyquist; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Censored data rank sum tests; Gehan s test; Generalized Wilcoxon test; Jackknifing; Two sample problem; Simulation; Survival data; Variance estimation; Influence function; Gross error sensitivity; Sensitivity curve; Misclassification; Statistics; computer and systems science; Statistik; data- och systemvetenskap; Statistics; statistik;

   Sammanfattning : In unbalanced small sample size problems with right censorings, the variance estmators of linear rank statistics, may be biased. This is the case with the commonly applied variance estimators for the generalized Wilcoxon rank test statistics of Gehan and Prentice. LÄS MER

7. 5. Aspects of analysis of small-sample right censored data using generalized Wilcoxon rank tests

   Författare :Marie-Louise Öhman; Hans Nyquist; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Censored generalized Wilcoxon rank test statistics; Variance estimation; Jackknifing; Influence function; Gross error sensitivity; Break-Down point; Sensitivity curve; Location parameter estimation; Product-Limit estimator and Monte-Carlo Simulation; Statistics; computer and systems science; Statistik; data- och systemvetenskap; Statistics; statistik;

   Sammanfattning : The estimated bias and variance of commonly applied and jackknife variance estimators and observed significance level and power of standardised generalized Wilcoxon linear rank sum test statistics and tests, respectively, of Gehan and Prentice are compared in a Monte Carlo simulation study. The variance estimators are the permutational-, the conditional permutational- and the jackknife variance estimators of the test statistic of Gehan, and the asymptotic- and the jackknife variance estimators of the test statistic of Prentice. LÄS MER