FRAME 39.
SUMMARY
1. Compute the population mean. The formula for the mean is u = ΣX. The procedure is adding
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the values of the data and dividing the total by the number of observations.
2. Subtract the mean from each value of the data. The formula is (X - u).
3. Square the difference between each value and the mean. The formula is
(X - u) 2 = (X - u) (X - u).
4. Add together the squared difference between each value and the mean.
The formula is Σ(X - u) 2.
5. Divide the total (of the squared difference between each value and the mean) by the number of
observations. The formula is Σ(X-u) 2
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This value is called the variance.
6. Take the square root of the variance which will result in the standard deviation.
Σ(X - U) 2
The formula is
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The standard deviation can thus be computed using the formula:
σ =
Σ(X - u) 2
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where σ (pronounced sigma) is the symbol used to represent population standard deviation.
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FI0921
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