Confidence Interval, Average expected Lifetime
October 6th, 2022
See attached file.
A GE flourescent bulb’s useful life is normally distrbuted. We wish to estimate the mean lifetime. A random sample of 15 bulbs are:
2,222 hrs standard deviation of 310 hrs
Refer to table 7A
a) Determine 95% confidence interval
b) If an executive can say the the average expected lifetime is 2,200, is he right?