Statistics for Big Data For Dummies
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Measures of central dispersion show how "spread out" the elements of a data set are from the mean. Three of the most commonly used measures of central dispersion include the following:

  • Range

  • Variance

  • Standard deviation


The range of a data set is the difference between the largest value and the smallest value. You compute it the same way for both samples and populations.


You can think of the variance as the average squared difference between the elements of a data set and the mean. The formulas for computing a sample variance and a population variance are slightly different.

Here is the formula for computing sample variance:


And here is the formula for computing population variance:


Standard deviation

The standard deviation is simply the square root of the variance. It's more commonly used as a measure of dispersion than the variance because it's measured in the same units as the elements of the data set, whereas the variance is measured in squared units.

About This Article

This article is from the book:

About the book authors:

Alan Anderson, PhD, is a professor of economics and finance at Fordham University and New York University. He's a veteran economist, risk manager, and fixed income analyst.

David Semmelroth is an experienced data analyst, trainer, and statistics instructor who consults on customer databases and database marketing.

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