Question.3194 - 8.3 Why is it not possible in Example 8.1 on page 256 to have 100% confidence? Explain. 8.19 The file Sedans contains the overall miles per gallon (MPG) of 2009 sedans priced under $20.000. 27 31 30 28 27 24 29 32 32 27 26 26 25 26 25 24 Source: Data extracted from “Vehicle Ratings,” Consumer Reports, April 2009, p. 27 a) Construct a 95% confidence interval estimate for the population mean MPG of 2009 sedans (4 cylinder) priced under $20.000, assuming a normal distribution. b) Interpret the interval constructed in (a). c) Compare the results in (a) to those in Problem 8.20 (a) 8.22 One of the major measures of the quality of service provided by any organization is the speed with which t responds to customer complaints. A large family-held department store selling furniture and flooring, including carpet, had undergone a major expansion in the past several years. In particular, the flooring department had expanded from 2 installation crews. The store had the business objective of improving its response to complaints. The variable of interest was defined as the number of days between when the complaint was made and when it was resolved. Data were collected from 50 complaints that were made in the last year. The data were stored in Furniture and are as follows: 54 5 35 137 31 27 152 2 123 81 74 27 11 19 126 110 110 29 61 35 94 31 26 5 12 4 165 32 29 28 29 26 25 1 14 13 13 10 5 27 4 52 30 22 36 26 20 23 33 68a) Construct a 95% confidence interval estimate for the population mean number of days between the receipt of a complaint and the resolution of the complaint. b) What assumption must you make about the population distrubiton in order to construct the confidence interval estimate in (a)? c) Do you think that the assumption needed in order to construct the confidence interval estimate in (a) is valid? Explain d) What effect might your conclusion in (c) have on the validity of the results in (a)? 8.23In New York State, savings banks are permitted to sell a form of life insurance called savings bank life insurance (SBLI). The approval process consists of underwriting, which includes a review of the application a medical information bureau check, possible requests for additional medical information and medical exams, and a policy compilation stage in which the policy pages are generated and sent tot the bank for delivery. The ability to deliver approved policies to customers in a timely manner is critical to the profitability of this service to the bank. During a period of one month, a random sample of 27 approved policies was selected, and the total processing time, in days, was a s shown below and stored in Insurance: 73 19 16 64 28 28 31 90 60 56 31 56 22 18 45 48 17 17 17 91 92 63 50 51 69 16 17a) Construct a 95% confidence interval estimate for the population mean processing time. b) What assumption must you make about the population distribution order to construct the confidence interval estimate in (a)? c) Do you think that the assumption needed in order to construct the confidence interval estimate in (a) is valid? Explain.
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It xx not xxxxxxxx to xxxx confidence xxxxxxx to xxxxxxxxx confidence xxx must xxx the xxxxxx infinite xxxxxx of xxxxx and xxx just xxx sheets xx paper xx used xx the xxxxxxx The xxxxxx sheets xx paper xxx to xx selected xxx confidence xxxxxxxx that xx would xxx from xxxxx confidence xxxx be xxxxx infinity xx plus xxxxxxxx which xx not xxxx useful xx estimating xx predicting xxx real xxxxxxxxxx The xxxxxxxx will xxxxxx include xxx required xxxx for xxxxx sheets xxx that xxxx always xxxxxxxx that xxx process xx working xxxxxxxx We xxx results xx only xxx sample xx determine xxx quality xxx manufacturer xxx never xxxx with xxxxxxxxxx that xxx result xx a xxxxxx includes xxx true xxxx of xxxxxxxxxx a xxxx n xxxxxxx of xxxxxxx Mean x For xxxxxxxxxx Z xxxxx Standard xxxxxxxxx sigma xxxxxxxxxx Interval xxxxx X xxxxxx Z xxxxx plusmn xxxxxx le xxxxx le x One xxx be xxxxxxxxx that xxx mean xxxxx per xxxxxx of xxxxxx sedans xxxxxx under xx somewhere xxxxxxx and x Since xxx confident xxxxxxxx for xxxxxxxxxx mean xxxxx per xxxxxx of xxxxx SUVs xxxx not xxxxxxx with xxxx for xxx population xxxx miles xxx gallon xx family xxxxxx we xxx confident xxxx the xxxxxxxxxx mean xxxxx per xxxxxx of xxxxx SUVs xx lower xxxx that xx family xxxxxx a xxxx n xxxx X xxxxxxx of xxxxxxx For xxxxxxxxxx Z xxxxx Standard xxxxxxxxx sigma xxxxxxxxxx Interval xxxxx X xxxxxx Z xxxxx plusmn xxxxxx le xxxxx le x The xxxxxxxxxx distribution xxxxx to xx normally xxxxxxxxxxxx c xxxxxx Probability xxxx Ecirc xxxxx Ecirc xxxxx r x eth x agrave x Iuml x frac x - x Z xxxxx Box-and-whisker xxxxxxxx From xxx normal xxxxxxxxxxx plot xxx the xxxxxxxxxxxxxxx plot xx can xx seen xxxx the xxxxxxxxxxxx is xxxxxx to xxx right x Even xxxxxx the xxxxxxxxxx distribution xx not xxxxxxxx distributed xxxx a xxxxxx of xxx t xxxxxxxxxxxx can xxxxx be xxxx due xx the xxxxxxx Limit xxxxxxx a xxxx n xxxxxxx of xxxxxxx Mean x For xxxxxxxxxx Z xxxxx Standard xxxxxxxxx sigma xxxxxxxxxx Interval xxxxx X xxxxxx Z xxxxx plusmn xxxxxx le xxxxx le x The xxxxxxxxxx distribution xxxxx to xx normally xxxxxxxxxxx c xxxxxx Probability xxxx - x - x Z xxxxx Box-and-whisker xxxxxxxx From xxx normal xxxxxxxxxxx plot xxx the xxxxxxxxxxxxxxx plot xx canbe xxxx that xxx distribution xx skewed xx the xxxxxMore Articles From Statistics
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