Unformatted text preview: Section 9.3 Handout
One-Tail Tests #944 The Glen Valley Steel Company manufactures steel bars. If the production
process is working properly, it turns out steel bars with mean length of at least 2.8 feet
with a standard deviation of 0.02 foot (as determined from engineering specifications on
the production equipment involved). Longer steel bars can be used or altered, but
shorter bars must be scrapped. You select a sample of 25 bars and the mean length is
2.73 feet. Do you need to adjust the production equipment? If you want to test the null hypothesis at the 0.05 level of significance, what decision
should you make? #945 You are the manager of a restaurant that delivers pizza to college dormitory
rooms. You have just changed your delivery process in an effort to reduce the mean
time between the order and completion of the delivery from the current 25 minutes.
From past experience, you can assume that the population standard deviation is 6 minutes. A sample of 36 orders using the new delivery process yields a sample mean of
22.4 minutes. Is there any evidence that the mean delivery time has been reduced below the previous
population mean value of 25 minutes? ...
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- Spring '08