## This is an approximate table of probabilities which relates
dispersion units above or below the mean value to the total
amount of the sample that is contained * outside * that region
for values less than zero and * inside * the region for values greater
than zero.

**
** Table of Probabilities |

-3.0 .001 | -2.5 .006 | -2.2 .014 |
-2.0 .023 | -1.8 .035 | -1.6 .055 |

-1.4 .081 | -1.2 .115 | -1.0 .158 |
-0.8 .212 | -0.6 .274 | -0.4 .345 |

-0.2 .421 | 0.0 0.500 | +0.2 .579 |
+0.4 .655 | +0.6 .725 | +0.8 .788 |

+1.0 .841 | +1.2 .885 | +1.4 .919 |
+1.6 .945 | +1.8 .965 | +2.0 .986 |

+2.2 .986 | +2.5 .994 | +3.0 .999 |

**
**

**
The use of this table is not complicated. Here is how it works.
**
Example 1:

You determine that some event lies +0.4 above the mean.
What is the probability that an event that large could happen.

- 65.5% of the sample is contained within that value. That means
100 -65.5 or 34.5% is outside of that range.
- The probability of an event at least that large happening is then
34.5% or approximately 1 out of 3.

Example 2

You determine that some event lies -1.6 below the mean.
What is the probability that an event this small could happen?

- If you are below the mean, the calculation is a bit easier.
-1.6 encloses 5.5% of the distribution. In other words
100 -5.5% = 94.5% of the time, the data values will be higher than
-1.6 below the mean.
- The probability of an event at least this small is therefore
5.5% or about 1 out of 20.