A dot plot is a graph that shows the frequency of data that occurs along a number line. Dot plots are a quick and easy way to organize your data, and are best used when comparing fewer than 25 different numbers. If you want to know how to make a dot plot, just look at step one below to get started.
Step 1. Collect your data
Your data is made up of the frequency with which a certain act or event occurs within a group of people or things. For example, let's say 10 students in a third grade class were asked the following question: "How many books did you read during the summer?" Your data represents the number of books each student read, regardless of which particular student read. What matters is knowing how many books each one read. So, let's say these are the ten different answers to the above question:
5, 1, 2, 5, 8, 0, 3, 2, 2, 1
Step 2. Organize your data in numerical order
Organizing the data from smallest to largest can help you interpret it and get a better sense and scope of the numbers you are working with. Take the numbers that you obtained from each student, in response to the question asked, and rearrange them from smallest to largest. You can cross out each number on the first list before writing it on the second. When you're done, check that you still have the same number of numbers (10). The list should look like this:
0, 1, 1, 2, 2, 2, 3, 5, 5, 8
Step 3. Create a horizontal line
Review your data and see which is the greatest and which is the least. The smallest number is 0 and the largest is 8, so you will have to draw a horizontal line that extends from 0 to 8. If you are working with a large range of numbers, you will not have to indicate each of them individually. However, for your purposes here, you can draw a horizontal line showing the numbers 0 through 8. The line should look like this:
0 1 2 3 4 5 6 7 8
Step 4. Write an “X” on the horizontal line each time a piece of information occurs
Write an “X” over the number 0 because this happens once, write 2 “Xs” over the number 1 because this happens twice, write 3 “Xs” over the number 2 because this happens 3 times, write 2 “Xs” over the number 5 because it happens twice, and write an "X" over the number 8 because it happens once. Now that you have created a dot plot of how often a class of 10 students reads a certain number of books, you can sit down and interpret your data.
Step 5. Interpret the data
Now that you have organized your data on a dot chart, you can take a look at some of its key components. This is what most people look for when interpreting a dot plot:
- The most frequent event. In this case, the most common was that the students read 2 books during the summer, since “2 books” occurred more frequently than any other data.
- Atypical data. "8" is an outlier because it is very far from the others, and breaks the pattern of the most common number of books read by students.
- Gaps There are gaps between “3 books” and “5 books” and between “5 books” and “8 books”.
- Clusters. There is clustering of data between “1 book” and “2 books,” which means that many of the students' responses fall between these two categories.