At a factory, batteries are produced with a standard deviation of 3.2 months. In a sample of 81 batteries, the mean life expectancy is 15.6 months. Find a 90% confidence interval estimate for the life...

Extracted text: At a factory, batteries are produced with a standard deviation of 3.2 months. In a sample of 81 batteries, the mean life expectancy is 15.6 months. Find a 90% confidence interval estimate for the life expectancy of all batteries produced at the plant. (15.523; 15.677) (15.535; 15.665) (14.903; 16.296) (15.015; 16.185)