CHAPTER 9 Summarizing and Graphing Your Data 111

Chapter 9

Summarizing and

Graphing Your Data

A

large study can involve thousands of participants, hundreds of variables,

and millions of individual data points. You need to summarize this ocean

of individual values for each variable down to a few numbers, called

summary statistics, that give readers an idea of what the whole collection of

numbers looks like — that is, how they’re distributed.

When presenting your results, you usually want to arrange these summary

statistics into tables that describe how the variables change over time or differ

between ­categories, or how two or more variables are related to each other. And,

because a picture really is worth a thousand words, you will want to display these

distributions, changes, differences, and relationships graphically. In this chapter,

we show you how to summarize and graph both categorical and numerical data.

Note: This chapter doesn’t cover time-to-event (survival) data, which is the topic

of Chapter 22.

IN THIS CHAPTER»

» ^{Representing categorical data»}

» ^{Characterizing numerical variables»}

» ^{Putting numerical summaries into}

tables»

» ^{Displaying numerical variables with}

bars and graphs