Squared deviations

Squared deviations from the mean (SDM) are involved in various calculations. In probability theory and statistics, the definition of variance is either the SDM expected value (when considering a theoretical distribution) or its average value (for actual experimental data). Computations for analysis of variance involve the partitioning of a sum of SDM.

An understanding of the computations involved is greatly enhanced by a study of the statistical value:

It is well known that for a random variable ${\displaystyle X}$ with mean ${\displaystyle \mu }$ and variance ${\displaystyle \sigma ^{2}}$,

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