Question

On a Saturday evening in Chicago, 34% of the people go out to dinner, 18% go out to see a movie, 13% go out to a party, and 35% stay home. If four people are randomly selected on Monday morning, what is the probability that all but one went out Saturday night?

Answer 1

100% for the conditions given.

Explanation:

P(out) = .34 + .18 + .13= 0.65

This is the probability for going out. The 4th person is the one not going out. We are to assume that he wants to watch Monday Night Football or something like it

So the probability of not going out for 1 person is 0.35

You can justify this in two ways.

Either you can rely on the given (P(stay at home) = 0.35)

or you can take the probability of the 3 given who do go out and subtract it from certainty (or 1)

1 - 0.65 = 0.35