For the variables describing the average number of cigarettes smoked during the past 3 months

(SMOKEP3M) and the variable describing the mother’s education (EDUMO) in the Parental HIV data determine the percent with missing values. For each of the variables describe hypothetical scenarios which might have led to these values being

a) missing completely at random,

b) missing at random, but not completely at random, and

c) neither missing completely at random nor missing at random.