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Measure of spread
A numerical value that describes how far data values are dispersed (spread out) within a distribution.
Standard deviation
The (population) standard deviation is the square root of the variance, that is, the square root of the mean of the squared deviations from the mean. For a population,
$$
\sigma=\sqrt{\frac{\sum(x-\mu)^2}{n}}
$$
Variance
The mean of the squared deviations from the mean. For a population,
$$\sigma^{2}=\frac{\sum(x-\mu)^{2}}{n}$$