\f1. [MODULE 11] A clinical trial was carried out comparing percutaneous transluminal coronary angioplasty (PCTA) with medical therapy in treating single-vessel coronary artery disease. Patients were given an exercise test 6 months following treatment. Excerise tests were per- formed up to maximal effort until symptoms such as angina appeared. The following table gives summary statistics regarding the change in length of time until adverse symptoms appeared: Treatment Therapy PCTA n 100 99 X 0.5 2.1 S 2.2 3.1 (a) Compute the pooled variance. (b) Compute the standard error of the difference between the treat- ment means. (c) Test the null hypothesis of equality of the treatment means at the a = 0.05 significance level. Give your test statistic, critical value, and degrees of freedom. (d) Compute the 95% confidence interval for the difference between the treatment means. (e) What are your conclusions