If the null hypothesis is true and we run the Mann-Whitney test on our data, the expectation is that
A) the difference scores will all be zero.
B) the test will be significant.
C) the sum of the ranks in the two groups will be approximately equal (assuming equal sample sizes).
D) the number of subjects in each group will be about the same.

Question

Quizplus · Accepted Answer

When the null hypothesis is true, the Mann-Whitney test does not find a significant difference between the two groups. One expectation when the null hypothesis is true is that the sum of the ranks in the two groups will be approximately equal, assuming equal sample sizes. Thus, the correct answer is C. The other choices are incorrect as they are not necessarily true when the null hypothesis is true.

If the Null Hypothesis Is True and We Run the Mann-Whitney