The Empirical Rule is also referred to as the 68-95-99.7% Rule. What it tells us is that for a normally distributed variable, the following are true: - Approximately 68% of the data lie within 1 standard deviation of the mean.
- Approximately 95% of the data lie within 2 standard deviations of the mean.
- Approximately 99.7% of the data lie within 3 standard deviations of the mean.
Most students find it easier to deal with the areas in each section of the curve, rather than the middle probabilities above: |

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