Question

The ages of a group of 121 randomly selected adult females have a standard deviation of 17.1 years. Assume that the ages of female

statistics students have less variation than ages of females in the general population, so let o = 17.1 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% 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
(Round up to the nearest whole number as needed.)

Answer 1

Answer: Start with the formula for Z:Z = (x-µ)/(σ/√n)We want the sample mean to be within one-half year of the population mean, so we set x-µ=0.5. We are looking for a 99% confidence interval, so we set Z=2.7578. We are told to use σ=18.1. Plugging those values into the formula, we get:2.5758 = 0.5(18.1/√n)We can rearrange to solve for n:((2.5758-18.1)/0.5)2 = nPlugging that into our calculator, we get n = 964.003. Since we can't have a fraction of a person in our sample, it would be safest to round up to n=965. (But since .003 is so small, I'd also accept 964 as an answer.)

probably wrong I don't know. (I think it is wrong)

Explanation: