Consider the data about the number of blocked intrusions in Exercise 8.1, p. 233. (a) Construct a 95% confidence interval for the difference between the average number of intrusion attempts per day before and after the change of firewall settings (assume equal variances). (b) Can we claim a significant reduction in the rate of intrusion attempts? The number of intrusion attempts each day has approximately Normal distribution. Compute P- values and state your conclusions under the assumption of equal variances and without it. Does this assumption make a difference? The numbers of blocked intrusion attempts on each day during the first two weeks of the month were 56, 47, 49, 37, 38, 60, 50, 43, 43, 59, 50, 56, 54, 58 After the change of firewall settings, the numbers of blocked intrusions during the next 20 days were 53, 21, 32, 49, 45, 38, 44, 33, 32, 43, 53, 46, 36, 48, 39, 35, 37, 36, 39, 45. Comparing the number of blocked intrusions before and after the change, (a) construct side-by-side stem-and-leaf plots; (b) compute the five-point summaries and construct parallel boxplots; (c) comment on your findings.