Suppose that a researcher goes to a small college with 200 faculty, 12 of which have blood type O-negative. She obtains a simple random sample of n = 20 of the faculty. Determine the mean and standard deviation of the number of randomly selected faculty that will have blood type O-negative.

Approach This is a hypergeometric probability experiment with N = 200, n = 20, and k = 12. We use Formula (2) to find the mean and the standard deviation, respectively.

Formula 2

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k N-n Myn and ox == N N 1 k N-k n.-. N N (2)