An Introduction

The mean is a very poor statistic. Does this statement surprise you? If it does, work through the following exercise.

Study this table of temperatures for 3 U.S. cities.

Maximum Temperature Means (Fahrenheit)
for 1961-1990

January July Yearly Mean
Fairbanks, AK -1.6 72.3 36.5
Phoenix, AZ 65.9 105.9 85.9
Honolulu, HI 80.1 87.5 84.4

Clearly the mean is not enough.

It needs a second statistic, the standard deviation, to make sense of these contradictions

Start with * Why We Need It * and learn about
this simple, yet powerful statistic.


Why We Need It

Calculating It and
Understanding It