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Unformatted text preview: mileage than the old engine at = 5% level? (Final 2003, Q2) A battery manufacturer claims that his company produces batteries with a mean life of 130 hours. An investigator working for an independent consumer protection agency wishes to test the credibility of the manufacturer’s claim. She randomly selects 100 batteries produced by the process and decides that she will believe the manufacturer’s claim only if the sample mean is not less than 129 hours. It is known that the standard deviation of the manufacturing process is 5 hours. (a) What is null hypothesis, alternative hypothesis? (b) What is the rejection region? (c) What is the level of significance of the test (α)? (d) If the investigator wishes to control the Type I error of the test to be 1%, what will be her rejection region? (e) If the sample mean of the 100 batteries that the investigator selected is 128 hours, what decision should she make at 1% level of significance?...
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 Spring '09
 AnthonyChan

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