A research council wants to estimate the mean length of time (in minutes) the average U.S. adult spends watching television using digital video recorders (DVRs) each day. To determine this estimate, the research council takes a random sample of 20 U.S. adults and obtains the times (in minutes) below.
From past studies, the research council assumes that σ is 4.3 minutes and that the population of times is normally distributed.
Use the information to construct the 90% and 99% confidence intervals for the population mean. Interpret the results and compare the widths of the confidence intervals. If convenient, use technology to construct the confidence intervals. |

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