a self-serve emissions inspection facility, drivers plug a cable into their car’s OBDII port. The kiosk reads emissions information from the car’s computer. Drivers follow on-screen instructions to complete the inspection and get their report. The standard deviation of inspection time has been 7.5 minutes. The facility recently redesigned the on-screen instructions to make them easier to follow and they want to check if this has reduced the standard deviation of inspection time. A random sample of 40 drivers showed a sample standard of inspection time to be 5.8 m

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Author:Amos Gilat
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At a self-serve emissions inspection facility, drivers plug a cable into their car’s OBDII port. The kiosk reads emissions information from the car’s computer. Drivers follow on-screen instructions to complete the inspection and get their report. The standard deviation of inspection time has been 7.5 minutes. The facility recently redesigned the on-screen instructions to make them easier to follow and they want to check if this has reduced the standard deviation of inspection time. A random sample of 40 drivers showed a sample standard of inspection time to be 5.8 minutes. At a 5% level of significance can we conclude that the redesign has reduced the standard deviation of inspection times? What is your conclusion at 1% significance? What is the population for which inferencing is being done?
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