Randall, Inc. is studying the rate of late payments by its commercial and retail customers. In a sample of 100 commercial customers taken last month, 17% were late with their payment. In a sample of 150 retail customers, 12% were late. 

a. Use the normal sampling distribution of sample proportion differences to test the hypothesis that there is no difference between the proportion of late payments in the two populations (commercial customers and retail customers) represented. Use a significance level of 5%. 

b. Compute the appropriate chi square statistic to test the hypothesis in part a. Compare your results to the results you produced in part a. 

c. Construct a proper table to conduct the chi square test in part b. Compare your results to the results you produced in parts a and b.