Posted by Anonymous on Wednesday, October 7, 2009 at 2:46pm.
A certain type of thermal battery for an airplane navigation device backup power has a mean life of 300 hours with a standard deviation of 15 hours. Assume a normal distribution of backup power device lives. What proportion of these batteries can be expected to have lives of 322 hours or less?

Math  bobpursley, Wednesday, October 7, 2009 at 2:52pm
What portion of the previous answer I gave did you not understand?