Thequality-control manager at a compact fluorescent light bulb(CFL) factory needs to determine whether the mean life of a large shipment of CFLs is equal to 7500 hours. The population standard deviation is 945hours. A random sample of 81 light bulbs indicates a sample mean life of 7,259 hours.

a. At the 0.05 level ofsignificance, is there evidence that the mean life is different from 7500hours?

b. Compute thep-value and interpret its meaning.

c. Construct a 95% confidence interval estimate of the population mean life of the light bulbs.

d. Compare the results of(a) and(c). What conclusions do youreach?

e. Compare the results of parts(a) through(d) to those when the standard deviation is 1,350 hours.