How large a sample should be taken if the population mean is to be estimated with 99% confidence to within $75? The population has a standard deviation of $900.

Answer 1

Thanks to Dr Bob for presenting this solution earlier : )

mu = bar x +/- 3(sigma/sqrt N)
mu is the population mean.
bar x is the average.
3 gives the 99% confidence interval.
sigma is standard deviation. N is the number of sample. Solve for N.