The mean annual cost of automobile insurance is $939 (CNBC, February 23, 2006).
Assume that the standard deviation is σ = $245.
a. What is the probability that a simple random sample of automobile insurance policies will have a sample mean within $25 of the population mean for each of the following sample sizes: 30, 50, 100, and 400?
b. What is the advantage of a larger sample size when attempting to estimate the population mean?