Standard Deviation

[SD Calculator]

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Formula

x = individual scores M = mean n = number of scores in group

Steps

Create two columns: x & (x-M)²

1. Put the raw data in the x column
2. Calculate the mean
3. Calculate deviation scores by subtracting each score from the mean and squaring it and put these in the second column
4. Sum the squared deviation scores
5. Set up the formula
6. Calculate s

Example

scores: 4,5,5,4,4,2,2,6

x	(x-M)2
4	0
5	1
5	1
4	0
4	0
2	4
2	4
6	4
M = 4	S(x-M)2 = 14
SD = 1.41

Practice by creating your own data and then check your work with the Virtual Statistician SD Calculator
(Only works with n = 8)