Answer to Question #59250 in Statistics and Probability for spenda

Question

The pharmaceutical company buys 400 batteries for running some specialist equipment. These batteries have a mean life of 120 hours and a standard deviation of 30 hours. Assume the battery life follows a normal distribution. [Use the Standard Normal table given in the Annexe for this task]

a) Use the standard normal table provided to calculate:
(i) the probability that a battery may work for less than 200 hours.
(ii) the probability that a battery may work for more than 200 hours.
(iii) the probability that a battery may work for less than 90 hours.

b) b) Find the number of batteries which have a life between 120 hours and 145 hours.