38630479-Ch8-Confidence-Interval-Estimation-Part2-Suggested-Problems-Solutions.doc - STATISTICS FOR SOCIAL SCIENCES BUS 152 CONFIDENCE INTERVAL

38630479-Ch8-Confidence-Interval-Estimation-Part2-Suggested-Problems-Solutions.doc

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STATISTICS FOR SOCIAL SCIENCES BUS 152 ___________________________________________________________________________ CONFIDENCE INTERVAL ESTIMATION 8.3 Confidence Interval Estimation for the Proportion Problem 8 (8.35)If you want to be 99% confident of estimating the population mean to within a sampling error of 20and the standard deviation is assumed to be 100, what sample size is required? Problem 9 (8.39)If the manager of a paint supply store wants to estimate the mean amount of paint in a 1-gallon can towithin 0.004 gallon with 95% confidence and also assumes that the standard deviation is 0.02gallon, what sample size is needed? _________________________________________________________________________________ Problem 10 (8.41)If the inspection division of a county weights and measures department wants to estimate the meanamount of soft-drink fill in 2-liter bottles to within 0.01 liter with 95% confidence and also assumesthat the standard deviation is 0.05 liter, what sample size is needed? SOLUTION:nZ22e21.962(0.05)2(0.01)2= 96.04Use n= 97 _________________________________________________________________________________ Problem 11 (8.43)An advertising agency that serves a major radio station wants to estimate the mean amount of timethat the station’s audience spends listening to the radio daily. From past studied, the standarddeviation is estimated as 45 minutes.a.What sample size is needed if the agency wants to be 90% confident of being correct to within minutes?b.If 99% confidence is desired, what sample size is necessary? 5 SOLUTION: a) n22e21.645245252= 219.19Use n= 220b) n22e22.58245252= 539.17Use n= 540 Z Z _________________________________________________________________________________

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