Problem 10.16 (b,c,d) Consider a study comparing two drugs for severe bladder infections. bladder infections. The variable x is the length of time to recovery (in days). For the n1 = 15 patients who received drug 1, we observed a mean recovery time of x1 = 16, 9 days. The mean recovery time was x2 = 19, 09 days for the n2 = 18 patients who received drug 2. Assume that the two recovery time populations are normally distributed with equal variances.

(b) Based on the output of R, calculate the value of the weighted standard deviation.

> t. test (x1, x2, var . equal=TRUE) Two Sample t-test data: x1 and x2 t = -5. 174, df = 31, p-value = 1.304e-05 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: