In a Mann-Whitney U test, U statistic was calculated to be 38.78 based on sample sizes of 24 and 20.What is the z value for this test?
A)0.133
B)-4.74
C)240
D)42.43
E)8.75

Question

Quizplus · Accepted Answer

The formula for the z-score in Mann-Whitney U test is z = (U - (n1*n2/2))/sqrt((n1*n2*(n1+n2+1))/12) where U is the test statistic, n1 and n2 are the sample sizes. Plugging in the given values, we get z = (38.78 - (24*20/2))/sqrt((24*20*(24+20+1))/12) = -4.74. Therefore, the answer is B.

In a Mann-Whitney U Test, U Statistic Was Calculated to Be