The Quality Control Manager at a Cell Phone Battery Factory

Multiple Choice

The quality control manager at a cell phone battery factory is interested in the mean life of a large shipment of batteries.Battery life is normally distributed with a standard deviation of 100 hours.A random sample of 64 batteries indicates a sample mean of 350 hours.The 99% confidence interval for mean battery life is _____.

A) [317.8,382.2]
B) [308.9,391.1]
C) [311.4,362.5]
D) [312.5,387.5]
E) [320.9,379.1]