Page 107 - Statistics for Dummies

Chapter 6
Getting the Picture: Graphing
Categorical Data
In This Chapter
▶ Making data displays for categorical data
▶ Interpreting and critiquing charts and graphs
ata displays, especially charts and graphs, seem to be everywhere,
Dshowing everything from election results, broken down by every con-
ceivable characteristic, to how the stock market has fared over the past few
years (months, weeks, days, minutes). We’re living in an instant gratification,
fast-information society; everyone wants to know the bottom line and be
spared the details.
The abundance of graphs and charts is not necessarily a bad thing, but you
have to be careful; some of them are incorrect or even misleading (some-
times intentionally and sometimes by accident), and you have to know what
to look for.

This chapter is about graphs involving categorical data (data that places
individuals into groups or categories, such as gender, opinion, or whether a
patient takes medication every day. Here you find out how to read and make
sense of these data displays and get some tips for evaluating them and spot-
ting problems. (Note: Data displays for numerical data, such as weight, exam
score, or the number of pills taken by a patient each day, come in Chapter 7.)

The most common types of data displays for categorical data are pie charts
and bar graphs. In this chapter, I present examples of each type of data dis-
play and share some thoughts on interpretation and tips for critically evalu-
ating each type.

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