The ages of a group of

156

randomly selected adult females have a standard deviation of

17.8

years. Assume that the ages of female statistics students have less variation than ages of females in the general population, so let

=17.8

years for the sample size calculation. How many female statistics student ages must be obtained in order to estimate the mean age of all female statistics students? Assume that we want

90%

confidence that the sample mean is within one-half year of the population mean. Does it seem reasonable to assume that the ages of female statistics students have less variation than ages of females in the general population?

The required sample size is