In a study, 28 adults with mild periodontal disease are assessed before and 6 months after implementation of a dental-education program intended to promote better oral hygiene. After 6 months, periodontal status improved in 15 patients, declined in 8, and remained the same in 5.
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
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, as assuming there are no ties.