Question: In a simple random sample of 100 electronic components produced by a certain method, the mean lifetime was 125 hours. Assume that component lifetimes are

In a simple random sample of 100 electronic components produced by a certain method, the mean lifetime was 125 hours. Assume that component lifetimes are normally distributed with population standard deviation

σ = 20 hours.

a. Construct a 98% confidence interval for the mean battery life.

b. Find the sample size needed so that a 99% confidence interval will have a margin of error of 3.

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