The problem with this defining formula for standard deviation is that you have to calculate the mean of the data before you can calculate its standard deviation. However, there is a calculational formula that is easier to use but less intuitive. It is


where

The Second of these formulas is the more complicated of the two. However, there are really just two big calculations in it.

  1. The summing of the x column which is denoted by
  2. The summing of the x squared column which is denoted by

Press this button to see what the calculations look like.

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