find out the probability that the sample mean will be less than 27.5 hours.
A certain long-life battery has an average life of 28 hours and standard deviation of 2.2 hours. For a random sample of 50 batteries, what is the probability that the sample mean would be less than 27.5 hours?
(1) 0.0399
(2) 0.0668
(3) 0.0339
(4) 0.0539
(5) 0.049