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S^2 = \frac{1}{n - 1} \sum_{i = 1}^n \left( X_i - \bar{X} \right)^2 S^2 symbol represents: sample varianceX_i symbol represents: random variable\bar{X} symbol represents: sample mean4 identifiers linking sample variance across the web's reference databases
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In probability theory and statistics, variance is a measure of dispersion, meaning it is a measure of how far a set of numbers are spread out from their average value. It is defined as the expected value of the squared deviation from the mean of a random variable. The standard deviation is the square root of the variance. Technically, it is the second central moment of a distribution, and the covariance of the random variable with itself, and it is often represented by , , , , or .