At the local plant, batteries are being produced with life expectancy which has a variance of 5.6 months squared. Assume the mean life expectancy in sample of 64 batteries is 12.35 months.
a. Determine the 90% confidence interval estimate of mean life expectancy for all batteries produced at this plant.
b. What would the 90% confidence interval estimate be if the sample mean had come from a sample of 100 batteries?