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Standard Deviation
by Oliver Pugh
About Standard Deviation:
Consider the marks scored in two tests shown below:
ENGLISH: 46 48 51 53 64 67 70
MATHS: 14 38 49 58 67 84 89
The mean in each test is 57, but the spread of marks in the tests is quite different! The mean just gives an indication of the central or typical value, wheras the spread or dispersion of the marks about the mean is more important.
One measure of spread of a variable x from the mean is called the deviation from the mean.
|x - mean| is the deviation of a variable x from the mean.(The absolute value is taken).
One of the most useful measures of dispersion is called the standard deviation.
Follow These Steps To Easily Calculate It:
1. Calculate the mean of the distribution.
2. Find the deviation of each variable (x) from the mean.
3. Square each deviation to make it positive.
4. Find the mean of these squared deviations.
5. Find the square root of the result.
Click the "HELP" button on the applet to find out what to do!!
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2002
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