Practical Data Analysis with JMP®

The Concept of a Distribution

When we have a collection of data, we generally focus attention on one or more variables—attributes of the individuals that make up the collection. This chapter presents several standard tools that we can use to examine how a variable varies, to detect the pattern of variation that a variable exhibits, and to look as well for departures from the overall pattern. When we speak of a variable's distribution, we are referring to a pattern of values. The distribution describes the different values the variable can assume, and how often it assumes each value.

In our first example, we'll consider the ways in which life expectancy differs around the world. The data we'll use come to us from the United Nations, which in ...