When comparing two groups in which each participant gets a score for each level of the ordinal independent variable (a within-groups design), the best nonparametric test to use is the:
A) paired-samples t test.
B) Mann-Whitney U test.
C) Wilcoxon signed-rank test.
D) Kruskal-Wallis H test.

Question

Quizplus · Accepted Answer

The Wilcoxon signed-rank test is the best nonparametric test to use in a within-groups design because it compares two related samples and accounts for the fact that the variables are ordinal. The paired-samples t test assumes normality, which may not be met in this case. The Mann-Whitney U test is used for two independent groups and the Kruskal-Wallis H test is used for three or more independent groups, so they are not appropriate for this within-groups design.

When Comparing Two Groups in Which Each Participant Gets a Score