Practical Data Analysis with JMP®

Summary Statistics for a Single Variable

Graphs are an ideal way to summarize a large data set and to communicate a great deal of information about a distribution. We can also describe variation in a quantitative variable with summary statistics (also called summary measures or descriptive statistics). Just as a distribution has shape, center, and spread, we have summary statistics that capture information about the shape, center, or spread of a variable.

Let's look at the distribution output for our sample of 2010 life expectancies in 195 countries of the world. Just below the histogram, we find a table of quantiles followed by a list of moments.

Figure 3.12. Quantiles and Moments

Quantile is a generic term; you may be more familiar with ...