The lifetime of a SuperTough AAA battery is normally distributed with mean of 28.5 hours and standard deviation of 5.3 hours. For a battery selected at random, what is the probability that the lifetime will be 25 hours or less?

Question

a. 0.7454
b. 0.6604
c. 0.2546
d. 0.3396

Answer 1

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

answer c. check it with the applet.