Question: In a sample of 60 electric motors, the average efficiency (in percent) was 85 and the standard deviation was 2. a. Find a 95% confidence

In a sample of 60 electric motors, the average efficiency (in percent) was 85 and the standard deviation was 2.

a. Find a 95% confidence interval for the mean efficiency.

b. Find a 99.5% confidence interval for the mean efficiency.

c. What is the confidence level of the interval (84.63, 85.37)?

d. How many thermostats must be sampled so that a 95% confidence interval specifies the mean to within ±0.35?

e. How many thermostats must be sampled so that a 99.5% confidence interval specifies the mean to within ±0.35?

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a X 85 s 2 n 60 z 025 196 The confidence interval is 85 196260 or 84494 85506 b X 85 s 2 n ... View full answer

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