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Wald-Wolfowitz Runs Test II01:17

Wald-Wolfowitz Runs Test II

The Wald-Wolfowitz runs test, commonly referred to as the runs test, is a nonparametric test used to assess the randomness of ordered data. The test evaluates the number of runs, which are consecutive sequences of similar elements within the data. If the number of runs is significantly higher or lower than expected, the data is considered non-random, indicating a detectable pattern or structure.
For binary data, runs are identified using symbols such as + and −, or equivalently, 1s and 0s. In...
Randomized Experiments01:13

Randomized Experiments

The randomization process involves assigning study participants randomly to experimental or control groups based on their probability of being equally assigned. Randomization is meant to eliminate selection bias and balance known and unknown confounding factors so that the control group is similar to the treatment group as much as possible. A computer program and a random number generator can be used to assign participants to groups in a way that minimizes bias.
Simple randomization
Simple...
Friedman Two-way Analysis of Variance by Ranks01:21

Friedman Two-way Analysis of Variance by Ranks

Friedman's Two-Way Analysis of Variance by Ranks is a nonparametric test designed to identify differences across multiple test attempts when traditional assumptions of normality and equal variances do not apply. Unlike conventional ANOVA, which requires normally distributed data with equal variances, Friedman's test is ideal for ordinal or non-normally distributed data, making it particularly useful for analyzing dependent samples, such as matched subjects over time or repeated measures from...
Test for Homogeneity01:23

Test for Homogeneity

The goodness–of–fit test can be used to decide whether a population fits a given distribution, but it will not suffice to decide whether two populations follow the same unknown distribution. A different test, called the test for homogeneity, can be used to conclude whether two populations have the same distribution. To calculate the test statistic for a test for homogeneity, follow the same procedure as with the test of independence. The hypotheses for the test for homogeneity can be stated as...
Wald-Wolfowitz Runs Test I01:17

Wald-Wolfowitz Runs Test I

The Wald-Wolfowitz test, also known as the runs test, is a nonparametric statistical test used to assess the randomness of a sequence of two different types of elements (e.g., positive/negative values, successes/failures). It examines whether the order of the elements in a sequence is random or if there is a pattern or trend present. This nonparametric test applies to any ordered data despite the population and sample data distribution, even if a higher sample size is available.
The test works...
Mechanistic Models: Compartment Models in Individual and Population Analysis01:23

Mechanistic Models: Compartment Models in Individual and Population Analysis

Mechanistic models are utilized in individual analysis using single-source data, but imperfections arise due to data collection errors, preventing perfect prediction of observed data. The mathematical equation involves known values (Xi), observed concentrations (Ci), measurement errors (εi), model parameters (ϕj), and the related function (ƒi) for i number of values. Different least-squares metrics quantify differences between predicted and observed values. The ordinary least squares (OLS)...

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Related Experiment Video

Updated: May 29, 2026

Development of an Individual-Tree Basal Area Increment Model using a Linear Mixed-Effects Approach
04:35

Development of an Individual-Tree Basal Area Increment Model using a Linear Mixed-Effects Approach

Published on: July 3, 2020

Permutation tests for random effects in linear mixed models.

Oliver E Lee1, Thomas M Braun

  • 1Department of Biostatistics, University of Michigan, Ann Arbor, Michigan 48109-2029, USA. oel@umich.edu

Biometrics
|September 29, 2011
PubMed
Summary

This study introduces novel permutation tests for linear mixed models, offering a practical solution for complex random effects inference. These methods provide accurate results in various settings, unlike traditional tests.

Related Experiment Videos

Last Updated: May 29, 2026

Development of an Individual-Tree Basal Area Increment Model using a Linear Mixed-Effects Approach
04:35

Development of an Individual-Tree Basal Area Increment Model using a Linear Mixed-Effects Approach

Published on: July 3, 2020

Area of Science:

  • Statistics
  • Biostatistics

Background:

  • Inference for random effects in linear mixed models is complicated by variance components at the boundary of the parameter space.
  • Standard hypothesis tests (Wald, score, likelihood ratio) do not follow a chi-squared distribution under the null hypothesis.
  • Existing solutions for complex hypotheses involving multiple random effects are often cumbersome and nonintuitive.

Purpose of the Study:

  • To develop alternative statistical tests for random effects in linear mixed models.
  • To provide accurate and practical inference methods, especially when standard tests fail.
  • To address the challenges posed by boundary parameter spaces in variance component testing.

Main Methods:

  • Proposed two permutation tests: one based on best linear unbiased predictors (BLUPs) and another on the restricted likelihood ratio test (RLRT).
  • Utilized weighted residuals, with weights derived from estimated among- and within-subject variance components.
  • Computed null permutation distributions by permuting residuals within and among subjects, ensuring validity in asymptotic and small samples.

Main Results:

  • Permutation tests demonstrated valid size and power across various simulation settings.
  • The proposed methods offer a robust alternative to traditional chi-squared based tests.
  • The tests were successfully applied to a real-world dataset of chronic myelogenous leukemia patients.

Conclusions:

  • Permutation tests provide a reliable and practical approach for hypothesis testing of random effects in linear mixed models.
  • These methods overcome the limitations of standard asymptotic tests when dealing with boundary null hypotheses.
  • The study offers valuable tools for statistical inference in complex longitudinal and clustered data analysis.