Tutoring statistics, I’m happy to add this method to my repertoire.  The tutor brings forth a shortcut for finding the standard deviation.

According to my source listed below, the standard deviation (σ) can be estimated as follows:

σ=range/6
The range is defined as the greatest-least values of the data set.

The reasoning behind the estimate is that, with a normal distribution, 99.7% of the data lies between µ-3σ and µ+3σ, µ being the mean, or center point, of the data.  (µ+3σ) – (µ-3σ)=µ+3σ-µ+3σ=6σ, but also equals the range. Since the range equals 6σ, σ=range/6.

In my next article, I’ll compare the standard deviation computed from the proper formula to what you get from the estimate above.  I’m as curious as you are:)

Source:

Zimmer, Cooke, et.al.  Mathematics of Data Management.  Toronto:   Nelson, 2003.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.