Question

IS UULIU DES possib The quality control manager at a light bulb factory needs to estimate the mean We of a large shipment of light bulbs. The standard deviation is 117 hours. A random sample of 81 he bulbs indicated a sample meant of 420 hours. Complete parts (a) through (d) below a. Construct a 95% confidence interval estimate for the population mean life of light bulbs in this shipment. The 95% confidence interval estimate is from a lower limit of hours to an upper limit of hours. (Round to one decimal place as needed.) b. Do you think that the manufacturer has the right to state that the lightbulbs have a meanife of 470 hours? Explain Based on the sample at the manufacture the right to that the lightbulbs have a mean of 470 hours. Amen of 470 hours is standard errors the sample that the lights have a mean le of 470 hours e. Must you assume that the population light bulbife is normally distributed? Explain O A Yes the sample size is too large for the samping debution of the mean to be approximately normal by the Central Limit Theorem OB. N incs is known the sampling debution of the mean does not need to be approximately distributed OC. No, non s on and the same size is large enough the samping dibution of the mean is approximately by the Centra OD Yes the sample i s not large enough for the samping distribution of them to be mately normal by the Central Theorem Therom. d i? d. Suppose the and deviation changes to hours. What are your a The con t ervals would be from a lower hours to per hours Based on the same and a handard deviation of the manufacturer at the t eam ofrohousAman 470 standard Click to select your awer