Sample variance
Sample variance is an estimator of variance. Given a sample
![[eq1]](http://images1.statlect.com/sample_variance__1.png)
of
observations, the sample variance can be computed either
as![[eq2]](http://images1.statlect.com/sample_variance__3.png)
or
as![[eq3]](http://images2.statlect.com/sample_variance__4.png)
where
is the sample
mean:![[eq4]](http://images2.statlect.com/sample_variance__6.png)
When the
observations are independent,
is a biased estimator of the population variance, while
is unbiased.
The lecture entitled Variance estimation provides more details about the sample variance.
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