Elementary Statistics Final Review Problem (1 Problem)?

Question by Scott: Elementary Statistics Final Review Problem (1 problem)?
4.
In a survey conducted by researchers at the University of Wisconsin, subjects were asked the question “Have you ever used cocaine?” in one of three methods, anonymous survey, personal interview, or phone survey. The contingency table below shows the results of this survey of 2400 students. Suppose one subject is randomly selected from this group. Find the probability that the subject answered “No” given that the subject participated in a phone interview. Show this answer as a fraction. Do not attempt to reduce the fraction.

Survey Method NO YES TOTAL
Anonymous 576 224 800
Personal 600 200 800
Phone 632 168 800
Total 1808 592 2400
Answer

Best answer:

Answer by Ron W
632/800

Once you’re given that the subject participated in a phone interview, the other methods (and numbers related to them) are irrelevant.

A more interesting question would be “Given that the subject said no, what is the probability that this subject participated in a phone interview?”

Know better? Leave your own answer in the comments!

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