Which of These Tests Is a Nonparametric Method to Compare

Multiple Choice

Which of these tests is a nonparametric method to compare two populations when the samples are matched pairs and the data are interval, and where the normality requirement necessary to perform the parametric test is unsatisfied?

A) the Wilcoxon rank sum test
B) the sign test
C) the matched pairs t test
D) the Wilcoxon signed-rank test