Refer to Exercise 4.12 about MBTI and alcohol drinking.

a. When the sample proportion of 0.092 who reported drinking alcohol frequently is the cutpoint for forming a classification table, sensitivity = 0.53 and specificity =

0.66. Explain what these mean, and show that the sample proportion of correct classifications was 0.65.

b. The MBTI data file also shows responses on whether a person smokes frequently.

When a classification table for the model containing the four main effect terms to predict smoking uses the sample proportion of frequent smokers of 0.23 as the cutoff, sensitivity = 0.48 and specificity = 0.55. The area under the ROC curve is 0.55. Does knowledge of personality type help you predict well whether someone is a frequent smoker? Explain.