. . Variance Variance is a statistical measure that tells us how measured data vary from the average value of the set of data. Mathematically, variance is the mean of the squares of the deviations from the arithmetic mean of a data set.
The terms variability, spread, and dispersion are synonyms, and refer to how spread out a distribution is. Definition . : (Variance) The variance of a random variable X denoted by Var or or ) or X V X σ σ is V X E X E X E X )) Square root of variance is called standard deviation . That is standard deviation V X ) .
The variance and standard deviation of a random variable are always non negative.