Suppose there are two samples of size 6 and 7, with a rank sum of 58 in the sample of size 6. Using the Wilcoxon rank-sum test, evaluate the significance of the results, assuming there are no ties?

Suppose patients are graded on the degree of change in periodontal status on a 7-point scale, with +3 indicating the greatest improvement, 0 indicating no change, and −3 indicating the greatest decline. The data are given in Table 9.9.

Table 9.9: Degree of change in periodontal status

Change score ______________ Number of patients

+3 ………………………………………. 4

+2 ………………………………………. 5

+1 ………………………………………. 6

0 ………………………………………... 5

−1 ………………………………………. 4

−2 ………………………………………. 2

−3 ………………………………………. 2