Dotplot Graphs

Introduction

A dotplot is a graph used to represent quantitative data. It consists of data points plotted above the x-axis, typically using dots. For relatively small amounts of data, dotplots are fairly easy to create and interpret.

Example

A high school history teacher recorded the test scores for 30 students on a recent exam. The score are listed below:

88, 90, 85, 83, 89, 85, 81, 85, 86, 88, 85, 90, 85, 81, 86, 82, 84, 82, 83, 95, 88, 91, 92, 86, 82, 81, 81, 75, 83, 84

Using the data above, construct a dotplot to better visualize and understand the data.

Solution:

1. Begin by sorting the data as shown below:

75, 81, 81, 81, 81, 82, 82, 82, 83, 83, 83, 84, 84, 85, 85, 85, 85, 85, 86, 86, 86, 88, 88, 88, 89, 90, 90, 91, 92, 95

2. Determine the maximum and mimumum values:

minimum: 75    maximum:95

3. Determine an easy to interpret range for your tick marks. For this example, creating an x-axis from 75 to 95, with tick marks spaced 5 units apart seems appropriate.

4. Place dots above the x-axis at the appropriate x locations. Also, make sure to stack the points when there are multiple values at any given location.

5. Make sure to label the main title and x-axis.