Chapter 8, Problem 2CRE

We want to estimate the mean IQ score for the population of college students. We know that for people randomly selected from the general population, the standard deviation of IQ scores is 15.

1. a. Using a standard deviation of 15, how many college students must we randomly select to take an IQ test if we want to have 95% confidence that the sample mean is within 3 IQ points of the population mean?
2. b. How is our estimate of the mean IQ score of college students affected if the sample size is larger than necessary? Smaller than necessary?
3. c. Is the actual standard deviation of IQ scores for college students likely to be equal to 15, more than 15, or less than 15? Explain. If we used the actual value instead of 15 in part (a), how would that answer be affected? Would it be the same, smaller, or larger?