In a random sample of 120 car batteries produced by a special method, the sample average...

In a random sample of 120 car batteries produced by a special method, the sample average lifetime was 135 hours and the sample standard deviation was 12 hours. An engineer claims that the mean lifetime is between 132.452 and 137.548 hours. Assume data is normally distributed.

(a) What level of confidence can this statement be made with?

(b) Create a confidence interval for the population variance and explain how you did it. State your conclusion.

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orchestra answered 1 year ago

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