In addition to their age levels, the movie audiences in Exercise 2 were also asked if they had seen the movie before (Never, Once, More than Once). Here is a table showing the responses by age group:

Under 6 6–9 10–14 15–21 Over 21 Never 39 60 84 16 151 Once 3 20 38 2 15 More Than Once 3 3 32 0 4

a) Find the marginal distribution of their previous viewing of the movie. (Hint: Find the row totals.)

b) Verify that the marginal distribution of the ages is the same as that given in Exercise 2.