The distributions of most continuous random variables will follow the shape of the normal curve.
Figure 1. |
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On the normal curve, mean, median, and mode all exist at the center.
Figure 2. |
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The graph changes direction at inflection points. These first points mark the distance of one standard deviation from the mean.
Figure 3. |
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The Empirical Rule |
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The empirical rule states that: 68% of all values fall within 1 standard deviation of the mean. 95% of all values fall within 2 standard deviations of the mean. 99.7% of all values fall within 3 standard deviations of the mean. |