Assignment:
AARP reported on a study conducted to team how long it takes in individual to prepare their federal income tax return(AARP Bulletin. April 2008). The data contained in the file named Tax Return are consistent with the study results. These data provide the time in hours required for 40 individuals to complete their federal income tax returns. Using past years' data the population standard deviation can be assumed known with σ = 9 hours. What is the 95% confidence interval estimate of the mean time it takes an individual to complete a federal income tax return?
Provide complete and step by step solution for the question and show calculations and use formulas.