How large a sample should be taken if the population mean is to be estimated with 99% confidence to within $72? The population has a standard deviation of $800.

Answer 1

mu = bar x +/- 2.58(sigma/sqrt N)
mu is the population mean.
bar x is the average.
2.59 gives the 99% confidence interval.
sigma is standard deviation. N is the number of sample. Solve for N.