Question

Duracell Ltd claim that the life of their batteries in motorised soft toys is approximately normally distributed with a mean of 93.3 hours and a standard deviation of 14.7 hours. The best 77% of batteries would last beyond how many hours? Answer correct to 2 decimal places.

Answer 1

Solution:

The data represent the life of their batteries in motorised soft toys is approximately normally distributed with a mean of 93.3 hours and a standard deviation of 14.7 hours .

The best 77% of batteries would last beyond number of hours is,

From the standard normal table, the indicated z score for the area of 0.7700 subtract from 1 and indicative area 0.2300 is - 0.73

x = + (z * )

= 93.3 + ( -0.73 * 14.7)

= 93.3 - 10.731

=82.56

The best 77% of batteries would last beyond number of hours is 82.56