variance

a measure of dispersion. the average squared distance from the mean.

It is often important to know how dispersed a set of scores are. If your doctor tells you that your cholesterol is 20 points higher than the average, what does that tell you? Should you be concerned? What if the doctor tells you that it is 200 points higher? However much higher than the average, the first question should be: is my score an extremely high score, or is it still within a normal range?

Knowing the variance helps to answer this question.

There are two kinds of variance, sample variance and population variance.

See our tutorial on "how to calculate variance" for practical step by step information on obtaining variance. Measures of central tendency such as average and mode