TThe quality control manager at a light bulb factory needs toestimate the mean life of a large shipment of light bulbs. Thestandard deviation is 108 hours. A random sample of 81 light bulbsindicated a sample mean life of 410 hours . a. Construct a 99%confidence interval estimate for the population mean life of lightbulbs in this shipment. b. Do you think that the manufacturer hasthe right to state that the light bulbs have a mean life of 410hours? Explain. c. Must you assume that the population light bulblife is normally distributed? Explain. d. Suppose that the standarddeviation changes to 80 hours. What are your answers in (a) and(b)?
