The quality control manager at a light bulb factory needs to estimate the mean life of a large shipment of light bulbs. The standard deviation is 80 hours. A random sample of 64 light bulbs indicated a sample mean life of 350 hours.

99% confidence interval estimate for the population mean life of light bulbs in this shipment lies between:

Select one:

a. (333.6 hours and 366.4 hours)b. (270 hours and 430 hours)c. (330.4 hours and 369.6 hours)d. (324.2 hours and 375.8 hours)