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Dot Plot in Statistics: Definition, Method & Examples

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  • 0:00 What Is a Dot Plot?
  • 1:23 Creating a Dot Plot
  • 2:03 Using Dot Plots
  • 3:29 Lesson Summary
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Lesson Transcript
Instructor: Mia Primas

Mia has taught math and science and has a Master's Degree in Secondary Teaching.

Dot plots are just one of the many methods used to organize statistical data. In this lesson, you will learn the definition of a dot plot, when it should be used, and how to create one.

What is a Dot Plot?

As a school teacher, Mr. Page likes to have snacks available to reward his students for good behavior. He took a poll on the first day of school to find out what kinds of snacks the students prefer. This table shows the results for one of his classes:

Preferred Snack Number of Students
Popcorn 8
Pretzels 4
M&M's 5
Twizzlers 6
Kit-Kats 3

While the table was an efficient way to display the data, Mr. Page wanted to present it in a more visual format, so he decided to create a dot plot.

A dot plot is a graphical display used in statistics that uses dots to represent data. Dot plots can be used for univariate data; that is, data with only one variable that is being measured. Dot plots are useful when the variable is categorical or quantitative. Categorical variables are variables that can be organized into categories, like types of sports, ice cream flavors, and days of the week. Quantitative variables, on the other hand, are variables that can be measured and have numerical values. Population, shoe size, and heart rate are examples of quantitative variables.

Dot plots work very well for data with a small number of values. They would not work well for large sets of data, because a dot would need to be plotted for each value. Histograms or box plots are more useful for large sets of data.

Creating a Dot Plot

To create a dot plot, we start by drawing a horizontal line with categories or numbers written beneath it. For the preferred snack results, Mr. Page wrote the names of each snack under the line. Then, he drew a dot above the line for each student who chose that particular snack. For example, he drew eight dots above popcorn, four dots above pretzels, five dots above M&M's, and so on. The numbers represent the frequency of each result, or how often the result occurs. Each dot represents one student, so the total number of dots is equal to the total number of students. In this example, there are 26 dots representing the snack choices for the 26 students.


Dot plot of preferred snack choice
dotplot1

Using Dot Plots

The students in Mr. Page's class enjoyed seeing the results of the snack survey displayed on the board, so he decided to create another dot plot, showing the number of siblings for each student. His class was able to identify some interesting information, such as the range, shape, and mode of the data.


Dot plot of number of siblings
dotplot2

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