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SAT - Math - Probability

The data in the table above were produced by a sleep researcher studying the number of dreams people recall when asked to record their dreams for one week.

The data in the table above were produced by a sleep researcher studying the number of dreams people recall when asked to record their dreams for one week. Group X consisted of 100 people who observed early bedtimes, and Group Y consisted of 100 people who observed later bedtimes. if a person is chosen at random from those who recalled at least 1 dream, what is the probability that the person belonged to Group Y?

Event X: A person chosen randomly recalls dream at least once

Event Y: Probability that the person belonged to Group Y

P(Y) = 100/200 = 1/2

P(X) = 1 - (15+21) / 200 = 1- 36/200 = 1-9/50 = 41/50

P(X|Y) = (11 + 68) / 100 = 79/100

P(