Question

The lifetime of a supertough aaa battery is normally distributed with mean of 28.5 hours and standard deviation of 5.3 hours. for a battery selected at random, what is the probability that the lifetime will be 25 hours or less?

Answer 1

To answer this item, we are first to determine the z-score of the presented data using the equation,

z-score = (x - μ) / σ

where x is the data, μ is the mean, and σ is the standard deviation.

Substituting the known values,

z-score = (25 - 28.5)/5.3

z-score = -0.66

This translates to a percentage equal to 25.46%.

Therefore, from the supertough aaa batteries, approximately 25.46% has a lifetime that is only about 25 hours or less.