Standard Deviation Definition:
Standard deviation is a statistical measure of spread or variability.The standard deviation is the root mean square (RMS) deviation of the values from their arithmetic mean.
Formula:
Standard Deviation
http://easycalculation.com/statistics/image/sd.jpg
Population Standard Deviation
http://easycalculation.com/statistics/image/popsd.jpg
where Σ = Sum of
X = Individual score
M = Mean of all scores
N = Sample size (Number of scores)
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