if the life in years of a washing machine is normally distributed with a mean of 15 years and a standard deviation of 1.6 years what should be the guarantee period if the company wants less than 1% of the machines to fail while under warranty

Question

if the life in years of a washing machine is normally distributed with a mean of 15 years and a standard deviation of 1.6 years what should be the guarantee  period if the company wants less than 1% of the machines to fail while under warranty

Steve · Answer

take a look here, and you can play with your numbers: http://davidmlane.com/hyperstat/z_table.html