5.6 Refer to the previous two exercises about MBTI and drinking.

a. The sample proportion who reported drinking alcohol frequentlywas 0.092.

When this is the cutpoint for forming a classification table, sensitivity =

0.53 and specificity = 0.66. Explain what these mean.

b. Using (a), show that the sample proportion of correct classifications was 0.65.

c. The concordance index c equals 0.658 for the model with the four main effects and the six interaction terms, 0.640 for the model with only the four main effect terms, and 0.568 for the model with only T/F as a predictor.
According to this criterion, which model would you choose (i) if you want to maximize sample predictive power (ii) if you think model parsimony is important?