A company makes batteries with an average life span of 300 hours with a standard deviation of 75 hours. Assuming the distribution is approximated by a normal curve fine the probability that the battery will last .

Question

Less than 250 hours

b. Between 225 and 375 hours

c. More than 400 hours

Answer 1

you can play around with Z table stuff at

http://davidmlane.com/hyperstat/z_table.html