Intermediate Computations

Random and independent samples of  recent prime time airings from each of two major networks have been considered. The first network aired a mean of  commercials during prime time, with a standard deviation of  commercials. The second network aired a mean of  commercials, with a standard deviation of  commercials. As the sample sizes are quite large, the population standard deviations can be estimated using the sample standard deviations. Construct a  confidence interval for , the difference between the mean number of commercials  aired during prime time by the first network and the mean number of commercials  aired during prime time by the second network. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal places. (If necessary, consult a list of formulas.)

What is the lower limit of the 99% confidence interval?

What is the upper limit of the 99% confidence interval?