O'Reilly logo

The Complete Idiot's Guide to Statistics, 2nd Edition by Robert Donnelly

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

The Empirical Rule: Working the Standard Deviation

The values of many large data sets tend to cluster around the mean or median so that the data distribution in the histogram resembles a bell-shape, symmetrical curve. When this is the case, the empirical rule (sounds like a decree from the emperor) tells us that approximately 68 percent of the data values will be within one standard deviation from the mean.
def•i•ni•tion
According to the empirical rule, if a distribution follows a bell-shape—a symmetrical curve centered around the mean—we would expect approximately 68, 95, and 99.7 percent of the values to fall within one, two, and three standard deviations around the mean respectively.
For example, suppose that the average exam score ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required