standard deviation
Post on 11-Jun-2015
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Standard Deviation is a number that describes how much data vary or spread out.
Uses difference of each data value from the mean.
The higher the number the more the data is spread out.
1. Find the mean,
2. Find the difference of each data value from the mean
3. Square each difference
4. Sum all the squared values
ix x
2ix x
x
21
n
ii
x x
5. Divide the sum by the number of data values minus one, (n – 1)
This value is called the variance,6. Finally take the square root to find the
standard deviation
22 1
1
n
ii
x xs
n
2s
21
1
n
ii
x xs
n
{6, 8, 9, 8, 7, 5, 6, 7, 6, 8}6 8 9 8 7 5 6 7 6 8
710
x
6 8 9 8 7 5 6 7 6 8
-1 1 2 1 0 -2 -1 0 -1 1
1 1 4 1 0 4 1 0 1 1
x x
2x x
x
21
14n
ii
x x
21 14
1.561 10 1
n
ii
x x
n
21 1.56 1.25
1
n
ii
x xs
n
Or just do it on your calculator!!!
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