SOLUTION: From past records it is known that the average like of a battery used in a digital clock is 305 days. The battery life is normally distributed. The battery was recently modified to

Question 617487: From past records it is known that the average like 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 deviation was 12 days. We want to test at the 0.05 level of significance whether the modification increase the life of the battery. What is our decision rule.
A) Do not reject the null hypothesis if computed t is 1.96 or greater.
B) Reject the null hypothesis if computed t is less that 1.96
C) Do not reject the null hypothesis if computed t is 1.729 or greater.
D) None of the above.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
From past records it is known that the average like 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 deviation was 12 days. We want to test at the 0.05 level of significance whether the modification increase the life of the battery. What is our decision rule.
A) Do not reject the null hypothesis if computed t is 1.96 or greater.
B) Reject the null hypothesis if computed t is less that 1.96
C) Do not reject the null hypothesis if computed t is 1.729 or greater.
D) None of the above.
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Ans: C
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Cheers,
Stan H.

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