Hi! I really need some help on this statistics question regarding sample sizes and probabilities of female ages. ANY Help would be greatly appreciated! thank you so much!

The ages of a group of 156 randomly selected adult females have a standard deviation of 18.2 years. Assume that the ages of female statistics students have less variation than ages of females in the general population, so let a = 18.2 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 95% condence 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 (Round up to the nearest whole number as needed.)