You work for a consumer advocate agency and want to find themean repair cost of

Question

You work for a consumer advocate agency and want to find themean repair cost of a washing machine. As part of your study,you randomly select 40 repair costs and find the meanto be $147.00. The sample standard deviation is$15.50. Complete parts (a) and (b).
A. construct a 90% confidence interval for the populationmean repair cost. (Round to three decimal places asneeded) B. Change the sample size to n=100. Construct a 90% confidenceinterval for the population mean repair cost. You work for a consumer advocate agency and want to find themean repair cost of a washing machine. As part of your study,you randomly select 40 repair costs and find the meanto be $147.00. The sample standard deviation is$15.50. Complete parts (a) and (b).
A. construct a 90% confidence interval for the populationmean repair cost. (Round to three decimal places asneeded) B. Change the sample size to n=100. Construct a 90% confidenceinterval for the population mean repair cost.

Explanation / Answer

n=40, xbar=147, s=15.5 =0.1, Z(0.05)=1.645 (check normal table) (a) The 90%CI is xbar±Z*s/n -->147±1.645*15.5/sqrt(40) --> ( 142.9685,151.0315) (b)n=100 The 90% CI is xbar±Z*s/n -->147±1.645*15.5/sqrt(100) --> (144.4503, 149.5497)

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