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Population versus Sample Standard Deviation
Home Introduction to the Standard Deviation Why do you need a measure of Variability? Measuring the Average Distance to the Mean Variability Quiz Population versus Sample Standard Deviation Standard Deviation Calculation Standard Deviation Calculation Short-Cut Method The Standard Deviation with Excel and The Online Calculator Standard Deviation in Practice Standard Deviation QuizView All Tutorials
 Standard Deviation Calculation Short-Cut Method
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: 7, 8, 10, 12, 16, 18, 19     Load another set of data

1Add up all the values.
Sum		 90
2Count the total number of values.
n 		7
3Divide the Sum by the the total number of values.
Mean		 12.9
4Subtract the mean from each value. Then Square that result.

ValueValue-Mean(Value-Mean)2
7 -5.9 34.8
8 -4.9 24
10 -2.9 8.4
12 -0.9 0.8
16 3.1 9.6
18 5.1 26
19 6.1 37.2
5Add up all the squared deviations.
Sum of Squared Deviations		 140.8
6Divide the Sum of Squared Deviations by n-1.
Sample Variance		 23.5
7Take the square root of the variance.
sample standard deviation		 4.8

Check Answers

 
Population versus Sample Standard Deviation
Home Introduction to the Standard Deviation Why do you need a measure of Variability? Measuring the Average Distance to the Mean Variability Quiz Population versus Sample Standard Deviation Standard Deviation Calculation Standard Deviation Calculation Short-Cut Method The Standard Deviation with Excel and The Online Calculator Standard Deviation in Practice Standard Deviation QuizView All Tutorials
 Standard Deviation Calculation Short-Cut Method

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April 17, 2010 | Marie wrote:
sample variance did not make sense. Divide the sum of squared deviations n-1
 
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 n-1 to get the sample variance?