Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.005) and its Z score.
99% = mean ± 2.575 SEm
SEm = SD/√n
Suppose we would like to estimate the mean amount of money spent on books by students in the fall semester. We have the following data from 400 randomly selected students: mean=$205 and s=$40. Assume that the amount spent on books by students is normally distributed. Compute a 99% confidence level for the population mean.
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