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3. In a sample of 125 electric motors, the average efficiency (in percent) was 88 and...

3. In a sample of 125 electric motors, the average efficiency (in percent) was 88 and the standard deviation was 2.

  1. Construct a 95% confidence interval on the mean μ.

  2. Construct a 99% confidence interval on the mean μ. This interval has higher confidence: how did the interval change as a result?

  3. If the interval is (87.50, 88.50), what is the level of confidence?

  4. How many motors would have to be sampled so that the 95% confidence interval specifies the mean to ±0.35?

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