The quality control manager at a light bulb factory needs to estimate the mean life of a large shipment of light bulbs. The standard deviation is 100 hours. A random sample of 64 light bulbs indicated a sample mean life of 350 hours.
A. Construct a 95% confidence interval estimate of population mean life of light bulbs in this shipment.
Answer: Z 1.96 325.50
B. Do you think that the manufacturer has the right to state that the light bulbs last an average of 400 hours? Explain. I do not believe that the manufacturer has the right to state that the light bulbs last an average of 400 hours because the mean of 400 hours shows the different on the 4 standard deviation and the answer that lead to 350 of hours is greater.
D. Suppose that the standard deviation changes to 80 hours. What are your answers? In (a) and (b)?
Step by step solutions to the problem is provided.