The quality control manger at a light bulb factory need to estimate the mean life of a large shipment of light bulbs. The SD is 100 100 hrs.A random sample of 64 light bulbs indicated a sample mean life of 350 hrs. a. Construct a 95% confidence interval e

The quality control manger at a light bulb factory need to estimate the mean life of a large shipment of light bulbs. The SD is 100 100 hrs.A random sample of 64 light bulbs indicated a sample mean life of 350 hrs.

a.Construct a 95% confidence interval estimate for the population mean life of light bulbs in this shipment.

b.Do you think that the manufacturer has the right to state that the light bulbs have a mean life of 400 hrs explain

c.Must you assume that the population light bulb life is normally distributed ?explain

d.Suppose that the SD change to 80 hrs what are your answers in a and b ?