Variance

The population variance is the average of the squared deviations from the mean. The sample variance is the sum of the squared deviations from the mean divided by one less than the number of data values.

Population Variance ( $image\popvar-sym.gif$ )

$image\popvar.gif$

Sample Variance (s2)

$image\samvar.gif$

where

$image\u.gif$	= Population Mean
$image\mean.gif$	= Sample Mean
N	= number of data values (for a population)
n	= number of data values (for a sample)
xi	= ith data value