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Standard deviation
The standard deviation is a measure of the amount of variation of a random variable expected about its mean.
Explanation
Population standard deviation (denoted by σ), for a finite set of numbers, is found by taking the square root of the average of the squared deviations of the values subtracted from their average value.
Sample standard deviation (denoted by s), uses the size of the sample as size of the population.
HistoryThe term standard deviation was first used in writing by Karl Pearson in 1894. |