Question

In a certain year, 88% of all Caucasians in the U.S., 73% of all African-Americans, 73% of all Hispanics, and 79% of residents not classified into one of these groups used the Internet for e-mail. At that time, the U.S. population was 64% Caucasian, 10% African-American, and 11% Hispanic. What percentage of U.S. residents who used the Internet for e-mail were Hispanic? (Round your answer to the nearest whole percent.)

Answer 1

Let A denote the event that the person uses internet for e-mail.

Let E1, E2, E3 and E4 denote the events that the person is Caucasian, African-American, Hispanic and does not classify in one othese groups respectively.

So,

Using Bayes' theorem,

Required probability =