The mean life of a particular brand of light bulb is 1000 hours and the standard deviation is 50 hours.Tests show that the life of the bulb is approximately normally distributed.It can be concluded that approximately 68% of the bulbs will last between ___.
A)900 and 1100 hours
B)950 and 1050 hours
C)850 and 1150 hours
D)800 and 1200 hours
E)1050 and 1250 hours

Question

Quizplus · Accepted Answer

According to the empirical rule, approximately 68% of the data falls within one standard deviation of the mean for a normal distribution. In this case, one standard deviation is 50 hours. Therefore, approximately 68% of the bulbs will last between (1000-50) hours and (1000+50) hours, which is 950 and 1050 hours. Choice B is the only one that includes this range of values.

The Mean Life of a Particular Brand of Light Bulb