Constructing Confidence Intervals In Exercises 45 and 46, usethe information to construct 90% and 99% confidence intervals forthe population mean. Interpret the results and compare the widthsof the confidence intervals.
45. DVR and Other Time-Shifted Viewing A group ofresearchers estimates the mean length of time (in minutes) theaverage U.S. adult spends watching television using digital videorecorders (DVRs) and other forms of time-shifted television eachday. To do so, the group takes a random sample of 30 U.S. adultsand obtains the times (in minutes) below.
29 12 23 24 33 24 28 31 18 27 27 32 17 13 17 12 21 32 26 16 2828 21 24 29 13 20 13 21 27Â Â
From past studies, the research council assumes that s is 6.5minutes. (Adapted from the Nielsen Company)
46. Sodium Chloride Concentrations The sodium chlorideconcentrations (in grams per liter) for 36 randomly selectedseawater samples are listed. Assume that s is 7.61 grams perliter.
30.63 33.47 26.76 15.23 13.21 10.57 16.57 27.32 27.06 15.0728.98 34.66 10.22 22.43 17.33 28.40 35.70 14.09 11.77 33.60 27.0926.78 22.39 30.35 11.83 13.05 22.22 13.45 18.86 24.92 32.86 31.1018.84 10.86 15.69 22.35
