Chapter 6, Problem 14TP

Solution

To State:

The approximate percentage of area under the normal curve that lies within two standard deviations of the mean.

  $95\%$

Concepts Used:

The empirical rule states that $99.7\%$ of the area under the normal curve occurs within three standard deviations of the mean, $68\%$ of the area occurs within one standard deviation of the mean, and 95% occurs within the two standard deviations of the mean.

Conclusion:

About $95\%$ of area under the normal curve lies within two standard deviations of the mean.