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S = \sqrt{S^2} S symbol represents: sample standard deviationS^2 symbol represents: sample variance2 identifiers linking sample standard deviation across the web's reference databases
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In statistics, the standard deviation is a measure of the amount of variation of the values of a variable about its (arithmetic) average. A low standard deviation indicates that the values of a set tend to be close to their average, while a high standard deviation indicates that the values are spread out over a wider range. Standard deviation may be abbreviated SD or std dev, and is most commonly represented in mathematical texts and equations by the lowercase Greek letter σ (sigma).