A study is done to see if ginseng improves memory. Volunteers are randomly replaced into the experimental or control group, and they partake in a series of memory tests.The experimental group of 120 subjects are then given a ginseng supplement, while the control group of 90 subjects are given a placebo. After 12 weeks, the tests are repeated, and the before and after scores of each subject are compared to see whether or not they showed improvement. In the first group,45 of the 120 subjects improved,While in the second group 27 out of the 90 improved.

a) Are these samples dependent or independent?

b) Test the claim that the proportions of improvement (p1 and p2) differ between the groups at a significance level of 0.05.