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

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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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Statistics For Engineers And Scientists

ISBN: 9780073401331

4th Edition

Authors: William Navidi

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Question Posted: Nov 01, 2018 08:16 AM

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

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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 the full answer

Statistics For Engineers And Scientists

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