Question

The life expectancy of a particular brand of lightbulb is normally distributed with a mean of 1,500 hours and a standard deviation of 75 hours.

What is the probability that a lightbulb will last less than 1,410 hours?


A .1151
B .2671
C .3321
D .4218
E .5111

Answer 1

Explanation:

14 10 is 90 less than the mean 1500

z score = - 90 / 75 = - 1.200

from a z-score table this represents .1151

or 11.51 % will last LESS than 1410 hrs