Choose an appropriate data display

Detailed Explanation: Choose an appropriate data display

The best data display depends on what kind of data you have and what you want to see.

• Bar graph: Use for categories, such as favorite sports or types of pets. The bars show how many are in each category.
• Dot plot: Use for individual numerical values, such as the number of books students read. Each dot represents one value.
• Histogram: Use for numerical data grouped into intervals, such as test scores grouped from $60$–$69$, $70$–$79$, and so on.
• Box plot: Use to summarize and compare numerical distributions by showing the center and spread.

Worked example

A teacher records the number of books read by $12$ students:

Step 1: Identify the type of data.

The data are numbers, so they are numerical data.

Step 2: Decide what the display should show.

There are only $12$ values, and we want to see each student’s number of books. The repeated values, gaps, and overall shape will be useful.

Step 3: Choose the display.

A dot plot is the best choice because it shows every individual value. A dot plot would look like this:

Number of books
 2   •
 3   ••
 4   •••
 5   •
 6   ••
 7   •
 8   •
 9
10   •

The three dots above $4$ show that three students read $4$ books. The empty space above $9$ shows that no student read $9$ books.

A bar graph would not be the best choice because the values are numerical, not categories. A histogram would be useful if there were many values grouped into intervals, and a box plot would be useful if we wanted only a summary of the center and spread.