1. The local lube shop advertises that it provides a complete lube-oil-filter maintenance service in just 20 minutes (or less) on average. You obtain a simple random sample of 144 lube-oil-filter service times. The sample average is 26 minutes with sample SD 12 minutes. Find a 95% confidence interval for the average lube-oil-filter service time. Based on your interval, do you think that the local lube shop's average service time is 20 minutes or less? Or do you think the average time is higher than 20 minutes? Explain.

MATLAB: An Introduction with Applications
6th Edition
ISBN:9781119256830
Author:Amos Gilat
Publisher:Amos Gilat
Chapter1: Starting With Matlab
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1. The local lube shop advertises that it provides a complete lube-oil-filter maintenance
service in just 20 minutes (or less) on average. You obtain a simple random sample of
144 lube-oil-filter service times. The sample average is 26 minutes with sample SD 12
minutes. Find a 95% confidence interval for the average lube-oil-filter service time.
Based on your interval, do you think that the local lube shop's average service time is 20
minutes or less? Or do you think the average time is higher than 20 minutes? Explain.
Transcribed Image Text:1. The local lube shop advertises that it provides a complete lube-oil-filter maintenance service in just 20 minutes (or less) on average. You obtain a simple random sample of 144 lube-oil-filter service times. The sample average is 26 minutes with sample SD 12 minutes. Find a 95% confidence interval for the average lube-oil-filter service time. Based on your interval, do you think that the local lube shop's average service time is 20 minutes or less? Or do you think the average time is higher than 20 minutes? Explain.
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