SOLUTION: From past records it is known that the average life of a battery used in a digital clock is 305 days. The battery life is normally distributed. The battery was recently modified to
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Question 150649: From past records it is known that the average life of a battery used in a digital clock is 305 days. The battery life is normally distributed. The battery was recently modified to last longer. A sample of 20 of the modified batteries was tested. It was discovered that the mean life was 311 days and the sample standard deviation was 12 days. We want to test at the 0.05 level of significance whether the modification increases the life of the battery. What is our decision rule? Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! From past records it is known that the average life of a battery used in a digital clock is 305 days. The battery life is normally distributed. The battery was recently modified to last longer.
Ho: u = 305
Ha: u > 305
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A sample of 20 of the modified batteries was tested. It was discovered that the mean life was 311 days and the sample standard deviation was 12 days.
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We want to test at the 0.05 level of significance whether the modification increases the life of the battery. What is our decision rule?
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Critical value for df=19 and alpha =5%: t = 1.729
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Reject Ho if the test statistic is greater than 1.729
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Cheers,
Stan H.
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