Question

The quality control manager at a lightbulb factory needs to estimate the mean life of a large shipment of lights. The process standard deviation is known to be 150 hours. A random sample 144 lightbulbs indicated a sample mean life of 750 hours.

a. Set up a 99% confidence interval estimate of the true population mean life of lightbulbs using this shipment.

b. Do you think that the manufacturer has the right to state that the lightbulbs last an average of 800 hours? Explain

c. Explain why an observed value of 650 hours for a single lightbulb is not unusual even though it may be outside of the confidence interval you calculated.

(Explain all answers thoroughly with work!)

Answer 1