The quality-control manager at a light bulb factory needs to determine whether the mean life of a large shipment of light bulbs is equal to 385 hours. The population standard deviation is 84 hours. A random sample of 49 light bulbs indicates a sample mean life of 367 hours.
A: at the 0.05 level of significance, is there evidence that the mean life is different from 385 hours?
B: Compute the p-value and interpret its meaning
C: Construct a 95% confidence interval estimate of the population mean life of light bulbs
D: Compare results of (a) and (c). What conclusions do you reach?
a) no meaningful conclusions can be reached
b) the results of (a) and (c) are no the same
c) the results of (a) and (c) are the same