Pie Charts

Pie charts are the most easily read charts.  They generally display one variable at a time and are thus univariate displays.  A simple pie chart displays the frequencies of different values of a variable as slices of a pie.  The bigger the slice, the more cases fall in that category.  Pie charts, therefore, work best when the number of values (and thus slices) is relatively small.  For example, if I wanted to describe the class status of students in some academic department, I might use a simple pie chart.

The big slice for Sophmore indicates that there are more cases in this category than any other.  Sophmore, therefore, is the mode.  Slices for Freshperson and Junior are also large while the slices for Senior and Graduate student are relatively small.

There are many forms of pie charts and some of these display two or more variables.  For example, if I wanted to show the total number of books owned by different classes of students, I might use the following pie chart:

In this pie chart, the size of the slice corresponds to how many books are owned by students in that class.  As you can see, seniors and graduate students own a lot of books despite being only a small fraction of the population.

SPSS instructions for a simple pie chart

SPSS instructions for a pie chart displaying more than one variable