6.39 Confidence interval mistakes and misunderstandings.
Suppose that 500 randomly selected alumni of the University of Okoboji were asked to rate the university’s academic advising services on a 1 to 10 scale. The sample mean was found to be 8.6. Assume that the population standard deviation is known to be .
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(a) She forgot to divide the standard deviation by . (b) Inference is about the population mean, not the sample mean. (c) Confidence does not mean probability; furthermore, making probability statements about doesn’t make sense because it’s fixed, not random. (d) The central limit theorem guarantees that the sample mean will be Normally distributed, not the original values. “… the sample mean of alumni ratings will be approximately Normal.”