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The Standard Deviation :: Standard Deviation Calculation Short-Cut Method
This method might be a bit faster to calculate. Calculate the Standard Deviation for the following data using the calculator to the right (round to 1 decimal points). Click on the Check Answer button to see how you did.

Data: 1, 3, 9, 12, 17, 18, 20     Load another set of data

1Add up all the values.
Sum
80
2Square this sum
Sum Squared
6400
3Count the total number of values.
n
7
4Divide Sum Squared by the the total number of values
Avg. Sum Squared
914.29
5Square each individual value. 
612 1
732 9
892 81
9122 144
10172 289
11182 324
12202 400
13Add up all these squared values.
Sum of Squares
1248
14Subtract Sum of Squares - Avg. Sum Squared 333.71
15Divide this by the total number of values minus 1.
sample variance
55.62
16Take the square root of the variance.
sample standard deviation
7.46

Check Answers

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