statistics
posted by b .
A sociologist is studying marriage customs in a rural community in Denmark to determine the age of the woman at the time of her first marriage. The sample standard deviation of these ages was 2.3 years. The sociologist wants to estimate the population mean age of a woman at the time of her first marriage. How large a sample is required to be 99% confident that the sample mean of ages is within 0.25 years of the population mean?

Use a formula to find sample size.
Here is one:
n = [(zvalue * sd)/E]^2
...where n = sample size, zvalue will be found using a ztable to represent the 99% confidence interval, sd = 2.3, E = 0.25, ^2 means squared, and * means to multiply.
Plug the values into the formula and finish the calculation. Round your answer to the next highest whole number.
Hope this helps.