Question

A company has developed a new type of light bulb, and wants to estimate its mean lifetime. A simple random sample of 12 bulbs had a sample mean lifetime of 739 hours with a sample standard deviation of 45 hours. It is reasonable to believe that the population is approximately normal. Find the lower bound of the 95% confidence interval for the population mean lifetime of all bulbs manufactured by this new process

Round to the nearest integer Write only a number as your answer. Do not write any units.

Answer 1

The lower bound of confidence interval is given by

Where

Where t is the table value from t distribution with n-1=11 degrees of freedom.

So the lower bound is

So the nearest integer is 710.

Thank you !!