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 7,503 hours. The population standard deviation is 100hours. A random sample of 64 light bulbs indicates a sample mean life of 7,478 hours.

a. At the 0.05 level ofsignificance, is there evidence that the mean life is different from 7,503hours?

b. thep-value and interpret its meaning.

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

a. Let be the population mean. the nullhypothesis, H0, and the alternativehypothesis, H1.

H0: =

7503

7503

H1:

7503

7503

What is the teststatistic?

What are the critical vlaue?