An accelerated life test on a large numberof type AAA reusab

An accelerated life test on a large numberof type -AAA reusable alkaline batteies revealed that the mean life for a particular use before they failed is 19.0 hours. The distruibution of the lives approximated a normal distribution. The sandard deviation of the distribution wa 1.2 hours . About 95.44 percent of the batteies failed between what two values?

A. 8.9 and 18.9

B. 16.6 and 21. 4

C. 12. 2 and 14.2

D. none of the above

E. 14.1 and 22.1

Solution

By empirical rule, 95.44% lie 2 standard deviations above or below the mean.

Thus,

u - 2sigma = 19 - 2*1.2 = 16.6
u + 2sigma = 19 + 2*1.2 = 21.4

Thus, OPTION B IS THE ANSWER. [ANSWER, B]