# Why is the empirical rule important?

Sep 21, 2017

The empirical rule, which states that nearly all data will fall within three standard deviations of the mean, can be useful in a few ways.

#### Explanation:

The empirical rule tells us about the distribution of data from a normally distributed population. It states that ~68% of the data fall within one standard deviation of the mean, ~95% of the data fall within two standard deviations, and ~99.7% of all data is within three standard deviations from the mean.

You can use the empirical rule to determine if your dataset follows a normal distribution . If you're given the mean and standard deviation of a normally distributed population, you can also determine what the probability is of certain data occurring .

For example, if the mean of a normally distributed data set is 56 and the standard deviation is 10, you know that 68% of your data will fall between 46 and 66 (one standard deviation below and above the average).

You can read more about the empirical rule here and see a slightly more complicated example of it being used here.