Comparing Circle Graphs,
Bar Graphs, and Tables

After completing this unit, you should be able to:

• Choose the most appropriate visual representation for data.

This unit is intended to review and clarify the uses for, and the similarities and differences between, tables, bar graphs, and circle graphs. Often it is difficult to determine the most appropriate way to visually display data. You may wonder whether you should use a table, circle graph or bar graph to display the given data. This section will help you learn how to choose the most appropriate graph, depending on the information you want conveyed.

While each representation has its strong points, each also has limitations. When we are representing data, it is important to determine which form is better. This will depend on what we want readers to be able to see.

• Tables are used to organize exact amounts of data and display information.
• Tables show numerical specifics rather than visual comparisons, and therefore take longer to read and understand.
• Using tables makes it more difficult to examine overall trends or comparisons than using bar and circle graphs.
• Circle graphs are used to compare parts to a whole. They visually represent data in the same proportion as the numerical data in a table.
• Constructing accurate circle graph is difficult particularly when the parts to whole relationships must be calculated and graphed without a computer.
• Bar graphs are used to compare data and show trends. They provide a display that enables the reader to quickly examine these trends visually.
• Bar graphs can be difficult to read accurately. A change in the interval and/or scale may alter the visual perception of data, which may persuade or trick the reader.

Now let's look at an example, to help illustrate this discussion.

Given the following table, draw the appropriate graph for each case, then answer the questions below.

1. Create a graph which best demonstrates the sales of each company.
2. Create a graph which best displays how much of the athletic shoe industry is dominated by Nike.
3. Describe the differences between the two graphical representations.
4. Compare them to the table shown above.
5. Come up with a case where it would be best to leave the information in a table?

If we want to make a graph that simply shows this data, it really wouldn't matter which type of graph we chose. The choice of graph depends on what we want to emphasize.

RECALL: Circle graphs are best used to compare parts to a whole, while bar graphs are most effective in comparing among groups.

1. Create a graph which best demonstrates the sales of each company.

   We are asked to show each company's sales. A bar graph which has the advantage of demonstrating countable data, facts about groups, and patterns is the best choice.

   Sneakers Sold This Month

   
   

2. Create a graph which best displays how much of the athletic shoe industry is dominated by Nike.

   We are to asked display Nike's role in the entire shoe industry. In other words, we want to display Nike as a part of the whole industry. The part to whole is best shown by using a circle graph.

   Sneakers Sold This Month (Total Sold = 100 Shoes)

3. Describe the differences between the two graphical representations.

   The overriding differences are:

   • The bar graph stresses the individual frequencies of each company as compared to the others.
   • The circle graph shows the entire amount sold.
   • The circle graph shows each company's sales as part of that whole.

In the circle graph, the five companies are presented as parts of the total industry, while the bar graph displays each company as its own entity, in competition with one another.

4. Compare them to the table shown above.

   Both displays are different from the table. They each visually display the data that is in the table, but they do it using two different methods. The circle graph utilizes the total from the table while the bar graph does not. Notice that each sector of the circle graph is the same proportion to the entire circle as the number of sales for that industry is to the entire amount of sales. The bar graph does not utilize the total from the table, but simply gives a visual listing of the information in the table. The number of sneakers sold per month are the same in the table as the height of the bars in the bar graph.

5. Come up with a case where it would be best to leave the information in a table?

   If you were asked to make exact calculations based on this data, a table would be best since you may take precise values directly from a table, without worrying about inaccuracies in the construction or reading of a graphs. A table would be the safest method of abstracting data for computations.

Now try the practice below. This unit includes one practice problem with detailed solutions. It is recommended that you read through this practice carefully, to help strengthen your sense of the distinction between, and the use of, circle and bar graphs.

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