An accelerated life test on a large number of type-D alkaline batteries revealed that the mean life for a particular use before they failed is 19.0 hours. The distribution of the lives approximated a normal distribution. The standard deviation of the distribution was 1.2 hours. About 95.44 percent of the batteries failed between what two values?
A) 8.9 and 18.9
B) 12.2 and 14.2
C) 14.1 and 22.1
D) 16.6 and 21.4
E) None of the choices are correct

Question

Quizplus · Accepted Answer

The correct answer is D.The z-score for 95.44% of the area under the normal curve is 1.96. So, the two values are 19.0 +/- 1.96 * 1.2, which is 16.6 and 21.4.

An Accelerated Life Test on a Large Number of Type-D