MandysNotes

The Normal Distribution

The Normal Distribution (1)

Friday, 22 January 2010 23:22

68-95-99.7 (Empirical) Rule

By

 

The EMPIRICAL RULE, otherwise known as the 68.26-95.44-99.74 RULE, says the following:

 

1) 68.26% of all observed data values will fall between ONE standard deviation to the RIGHT or LEFT of the mean. 

2) 95.44% of all observed data values will fall between TWO standard deviations to the RIGHT or LEFT of the mean. 

3) 99.74% of all observed data values will fall between THREE standard deviations to the RIGHT or LEFT of the mean. 


This is what the illustrated version of the Empirical Rule looks like:



EXAMPLE:

If we are told that the mean of our data is 100, and the standard deviation is 10, then we know the following:

1) 68.26% of our data will fall between 90 and 110. 

2) 95.44% of our data will fall between 80 and 120. 

3) 99.74% of our data will fall between 70 and 130. 

 

Disclaimer: I did not create nor do I own these videos.  I have simply embedded them, courtesy of YouTube.

NOTRad