In taking a sample of a observations from a population of N members, the variance of the sampling distribution of the sample mean is The quantity (N-n) (N-1) R N- N-1 is called the "finite population correction factor."

(a) To get some feeling for possible magnitudes of the finite population correction factor, calculate it for samples of n = 20 observations from populations of N-20, 40, 100, 1,000, and 10,000 members.

(b) Explain why the result for N-20, found in part (a), is precisely what one should ex- pect on intuitive grounds.

(c) Given the results in part (a), discuss the practical significance of using the finite popu- lation correction factor for samples of 20 observations from populations of different sizes.