Variance:
In statistics: A measure of the dispersion
of the values of a statistical variable. The standard formula for variance in
statistics is the mean square deviation of their average (in the sense of
mean):
Variance of X = σ2 = 1/N Σi
(Xi - Average of X)2
Average of X = 1/N Σi (Xi)
Here the average of a collection of data X1 ... XN
is the sum of their values divided by their number N and their variance
is the average squared deviation from the average. Of course the more and the
greater these differences from the average the greater the variance in the
collection. The σ stands for the standard
deviation, and thus the standard deviation is the (positive) root from
the variance, taking roots.
In statistics there is a whole set of
techniques called "Analysis of Variance" a.k.a. ANOVA that is concerned with
inferences that concern the variance. It is useful and important because
contributory factors in an effect of something influence the variance. |
