Standard Deviation

 = Mean 

Σ = Sum of

When dealing with a set of data you might use the mean and range. This is not always appropriate, as two sets of data can give you the same mean and range but be completely different!

Example:

1 2 4 8 10  Mean: 5 Range: 9

1 1 3 10 10 Mean:5 Range 9

They have the same mean and range but are spread out in a completely different way. To be able to make this difference more obvious we use Standard Deviation.

Standard Deviation shows how close the numbers in a set of data are to the mean. Theoretically, it would make sense to just take the mean away from each number. 

Example:

1 2 3 8 10

 1-5 =-4           2-5=-3           4-5=-1…