The Wilcoxon rank sum test assumes that the measurement scale of the data be at least:
A) nominal.
B) ordinal.
C) interval.
D) ratio.
E) Any measurement scale can be used for the Wilcoxon rank sum test.

Question

Quizplus · Accepted Answer

The Wilcoxon rank sum test is a nonparametric test for comparing two independent groups. Nonparametric tests do not make assumptions about the population distribution, but they do require a minimum level of measurement scale. The Wilcoxon rank sum test requires at least ordinal data because the test is based on ranking the observations in each group and comparing the distributions of ranks between the two groups. Nominal data would not be appropriate because there is no natural order to the categories, and interval/ratio data would be overkill because the test does not make use of the specific numerical values, only their order.

The Wilcoxon Rank Sum Test Assumes That the Measurement Scale