posted by Mark .
LongLast Inc. produces car batteries. The mean life of these batteries is 60 months. The distribution of the battery life closely follows the normal probability distribution with a standard deviation of 8 months.
As part of its testing program, LongLast tests a sample of 25 batteries.
What is the standard error of the mean?
That does not help calculate the standard of error.
8/sqrt(25) = 8/5 = 1.6