Empirical Rule
The empirical rule is only valid for bell-shaped (normal) distributions. The following statements are true.
- Approximately 68% of the data values fall within one standard deviation of the mean.
- Approximately 95% of the data values fall within two standard deviations of the mean.
- Approximately 99.7% of the data values fall within three standard deviations of the mean.
- The empirical rule will be revisited later in the chapter on normal probabilities.
