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The Standard Deviation :: Standard Deviation Calculation
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:
4, 9, 11, 12, 15, 19, 20
1
Add up all the values.
Sum
90
2
Count the total number of values.
n
7
3
Divide the Sum by the the total number of values.
Mean
12.9
4
Subtract the mean from each value. Then Square that result.
Value
ValueMean
(ValueMean)
^{2}
4
8.9
79.2
9
3.9
15.2
11
1.9
3.6
12
0.9
0.8
15
2.1
4.4
19
6.1
37.2
20
7.1
50.4
5
Add up all the squared deviations.
Sum of Squared Deviations
190.8
6
Divide the Sum of Squared Deviations by n1.
Sample Variance
31.8
7
Take the square root of the variance.
sample standard deviation
5.6
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September 9, 2013  Megan Garcia wrote:
why does the calculator say that 1212.9=0.9000000000000004 ?
February 2, 2013  Elsy wrote:
Great explanation, tools and visuals. Thank you.
June 12, 2012  Dennis wrote:
How do I divide in step 6
April 17, 2010  Marie wrote:
sample variance did not make sense. Divide the sum of squared deviations n1
September 21, 2009  anonomous wrote:
This was an excellent tutorial on stsndard deviation. Thank Y
September 15, 2009  Dave Mills wrote:
Excellent course! Thnak you!
March 18, 2009  Omar wrote:
Why do you divide the Sum of Squared Deviations by n1 to get the sample variance?