Question: A random sample of 91 light bulbs had a mean life of days with a standard deviation of days.

a) Calculate an interval estimate for the mean life, , of light bulbs of this type. In other words, construct a 90% confidence interval for the mean life, , of light bulbs of this type. SW (4 points)

b) Write the confidence interval in terms of a probability statement. Interpret the confidence interval in words. SW (3 points)