The lifetime of a type of hand phone battery is found to be normally distributed with mean 2.5 years and standard deviation 0.5 year. If a battery is randomly chosen, show that the probability the battery will last less than two years is 0.1587.
a) If a customer buys 5 batteries, what is the probability that 3 of the batteries will last less than two years?
a) If a customer buys 5 batteries, what is the probability that 3 of the batteries will last less than two years?