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% 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

Question

Quizplus · Accepted Answer

The 95.44% range in a normal distribution corresponds to approximately ±2 standard deviations from the mean. The mean is 19.0 hours, and the standard deviation is 1.2 hours. Therefore, the range is from 19.0 - 2(1.2) = 16.6 hours to 19.0 + 2(1.2) = 21.4 hours.

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