Asked by shani

A survery of 80 randomly selected companies asked them to report the annual income of their presidents. Assuming that incomes are normally distributed with a standrad deviation of #30,000, determine the 90% confidence interval estimate of the mean annual income of all company presidents.
Answered by PsyDAG
90% confidence interval = mean ± 1.645 SEm

SEm (Standard Error of the mean) = SD/√(n-1)