2.1.1.2 - Visual Representations

Frequency tables, pie charts, and bar charts are the most appropriate graphical displays for categorical variables. Below are a frequency table, a pie chart, and a bar graph for data concerning Penn State’s undergraduate enrollments by campus in Fall 2017.

Note that in the bar chart, the bars are separated by a space. The spaces between the bars signify that this is a categorical variable. On the following pages you will learn how to make these graphs using Minitab Express.

Frequency Table

A table containing the counts of how often each category occurs.

Tally
Campus Count Percent
University Park 40835 48.5%
Commonwealth Campuses 29388 34.9%
PA College of Technology 5465 6.5%
World Campus 8513 10.1%
Total 84201 100.0%

Penn State Fall 2017 Undergraduate Enrollments

Pie chart

Graphical representation for categorical data in which a circle is partitioned into “slices” on the basis of the proportions of each category.

Pie Chart of Campus
Category
  •  University Park (48.5%)
  •  Commonwealth Campuses (34.9%)
  •  PA College of Technology (6.5%)
  •  World Campus (10.1%)
Penn State Fall 2017 Undergraduate Enrollments
Bar chart

Graphical representation for categorical data in which vertical (or sometimes horizontal) bars are used to depict the number of experimental units in each category; bars are separated by space.

Minitab Express Bar Chart for Fall 2017 Penn State Undergraduate Enrollments

Penn State Fall 2017 Undergraduate Enrollments

Tips

Pie charts tend to work best when there are only a few categories. If a variable has many categories, a pie chart may be more difficult to read. In those cases, a frequency table or bar chart may be more appropriate.

When selecting a visual display for your data you should first determine how many variables you are going to display and whether they are categorical or quantitative. Then, you should think about what you are trying to communicate. Each visual display has its own strengths and weaknesses. When first starting out, you may need to make a few different types of displays to determine which best communicates your data.