A nonprofit bank that provides loans to small entrepreneurs in developing countries is considering organizing a mandatory training on good financial practices for all its loan-takers. To verify whether attending the course affects the chance that borrowers repay their short-term debt, two years ago the bank randomly split 2400 loan applicants into a group of 1200 subjects that received the mandatory training and a group of 1200 subjects that didn't receive it. The repayments of these 2400 loans were due last month. The bank is now looking at the following table, that indicates how many loan-takers in the two groups have repaid/not repaid their loan:

Repaired Not repaid
Trained 789 411
Non- trained 632 568

a. Of trained subjects, the proportion who repaid the loan was
b. Of non-trained loan-takers, the proportion who repaid the loan was
c. What is a 95% confidence interval for the difference between the proportion of trained and non- trained loan-takers who repaid the loan?
d. Based on your previous answer, if we conduct a test of the null hypothesis that the proportion of trained and non-trained loan-takers who repaid the loan are the same against the alternative hypothesis that they differ, what decision would we make?