### Statistics: Mean life of light bulb with 90% confidence interval, distribution of worker insurance claims by day of week.

A random sample of light bulbs had a mean life of xbar = 587 hours. the standard deviation of the lifetime of all such light bulbs is of sigma = 36 hours #1 construct a 90% confidence interval estimate of the mean life, m, of all light bulbs of this type. It was expected that the mean lifetime of the bulbs was 600 hours.