A Mann-Whitney U test was performed to determine if there were differences in the cost of tuition at a Texas state university versus an Oklahoma state university.The total cost, including room, board, and books for 24 freshmen attending a Texas university were computed and compared to the total cost for 20 Oklahoma state university students.The U statistic was calculated to be 38.78 based on the 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 z value for a Mann-Whitney U test can be calculated using the formula z = (U - meanU) / SD, where meanU = n1 * n2 / 2 and SD = sqrt(n1 * n2 * (n1 + n2 +1) / 12). Plugging in the values from the problem, we get z = (38.78 - 240) / 42.43 = -4.74. Therefore, the answer is choice B.

A Mann-Whitney U Test Was Performed to Determine If There