A light bulb manufacturer wants to compare the mean lifetimes of two of its light bulbs,...

Transcribed Image Text:

A light bulb manufacturer wants to compare the mean lifetimes of two of its light bulbs, model A and model B. Independent random samples of the two models were taken. Analysis of 11 bulbs of model A showed a mean lifetime of 1227 hours and a standard deviation of 86 hours. Analysis of 15 bulbs of model B showed a mean lifetime of 1379 hours and a standard deviation of 91 hours. Assume that the populations of lifetimes for each model are normally distributed and that the variances of these populations are equal. Construct a 95% confidence interval for the difference u,-u, between the mean lifetime u, of model A bulbs and the mean lifetime u, of model B bulbs. Then complete the table below. Carry your intermediate computations to at least three decimal places. Round your responses to at least two decimal places. (If necessary, consult a list of formulas.) What is the lower limit of the 95% confidence interval? What is the upper limit of the 95% confidence interval? A light bulb manufacturer wants to compare the mean lifetimes of two of its light bulbs, model A and model B. Independent random samples of the two models were taken. Analysis of 11 bulbs of model A showed a mean lifetime of 1227 hours and a standard deviation of 86 hours. Analysis of 15 bulbs of model B showed a mean lifetime of 1379 hours and a standard deviation of 91 hours. Assume that the populations of lifetimes for each model are normally distributed and that the variances of these populations are equal. Construct a 95% confidence interval for the difference u,-u, between the mean lifetime u, of model A bulbs and the mean lifetime u, of model B bulbs. Then complete the table below. Carry your intermediate computations to at least three decimal places. Round your responses to at least two decimal places. (If necessary, consult a list of formulas.) What is the lower limit of the 95% confidence interval? What is the upper limit of the 95% confidence interval?