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A measure of spread for a distribution of a numerical variable that determines the degree to which the values differ from the mean. If many values are close to the mean then the variance is small and if many values are far from the mean then the variance is large.
It is calculated by the average of the squares of the deviations of the values from their mean.
The variance can be influenced by unusually large or unusually small values.
The positive square root of the variance is equal to the standard deviation.
It is recommended that a calculator or software is used to calculate the variance. On a calculator the square of the standard deviation will give the variance.
See: measure of spread, sample variance, standard deviation
Curriculum achievement objectives references
Statistical investigation: Levels (7), (8)
