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Confidence interval for mean.

The life in hours of a 75 watt light bulb is known to be normally distributed with std deviation of 25 hours. A random sample of 20 bulbs has a mean life of 1014 hours.

a) Construct a 95% two sided confidence interval on the mean life.

b) Construct a 95% lower-confidence bound on the mean life.

Compare the lower bound of this confidence interval with the one from part a

Solution Summary

Step by step method for computing confidence interval for mean is given in the answer.