Use the blood pressure data in Table 9.2 that was described in Exercise 10 of Sec. 9.6. Suppose now that we are not confident that the variances are the same for the two treatment groups. Perform a simulation of the sort done in Example 12.3.8 to obtain a sample from the posterior distribution of the parameters when we allow the variances to be Unequal.
a. Draw a plot of the sample c.d.f. of the absolute value of the difference between the two group means.
b. Draw a histogram of the logarithm of the ratio of the two variances to see how close together they seem to be.