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What is a Dot Plot?
Dot Plots (also known as strip plots or dot charts) are simplified histograms that are used in statistics to analyze small data sets. It shows values falling into discrete categories. Because the “bars” of dots are equal in height to the number of items within a category, a dot plot can be compared to a bar graph. You will need to count the number of data points that fall in each bin before you can draw a stack with dots that are high for each bin. The good news is that you can also easily learn how to make a dot plot in Excel.
Data is encoded in dots or small circles using a dot plot. A number line displays the distribution of numerical variable values where each dot represents a value.
Types of Dot Plots:
There are three common variations of the dot plot:
The first I would refer to as a “traditional dot plot” (labeled simply “dot chart” above). This graph has been around since the beginning of time. These graphs were created by hand and show how data is distributed. These can be helpful if you need to visualize your data to identify outliers or get a feel for the shape. This is like a histogram, which encodes data distributions in bars and not as dots. The dots in this dot plot represent a single data point and don’t have to be evenly spaced along the horizontal line. These plots work best with small data sets. However, if you have more data than that, a histogram, box plot, or box plot may be more appropriate.
The most common one that I see in a business setting today is the one created by William S. Cleveland. Sometimes referred to simply as the Cleveland dot chart. This graph encodes quantitative data across categories. It can be thought of as an alternative to the bar charts. You can see my point of view in the following example by storytellingwithdata.com:
To create a dot plot, you don’t need to go through the entire process. This example illustrates how a dot plot works by moving to it from something familiar.
You don’t need to use the third view. There are other formatting options that we might consider. We could, for example, label each value within each dot. This would eliminate the need to use the x-axis. To give the graph more structure, we might add lines or gridlines from each category to its dot. This is commonly known as a “lollipop chart”
In this illustration, I used a horizontal version. However, you can also rotate the dots (imagine them replacing a vertical bar graph in a similar fashion to what I have illustrated). The data, length of category names and other elements will all play a role in the orientation you choose. It can be worthwhile to look at both horizontal and vertical layouts in order to decide which one makes sense in the situation.
Another common variant is the connected dots plot. The connected dot plot works in the same manner as the Cleveland dot plot, but it graphs two or more data series. Let’s continue the example, but now we’ll add another data series.
How to Make a Dot Plot?
After we’ve covered common types and shown a few examples, you might be asking, “How can I make one?”. Some tools include functionality to create them. Even if the tool doesn’t have this functionality, sometimes a little creativity can make it possible to create one.
You can create a Cleveland dots plot in Excel, for example. You can choose to have your data values in either horizontal or vertical orientation. Then, input the values for the other to create your categories. For example, in the horizontal Cleveland type that I explained in my explanation, the x-values of the scatterplot are mine data values, and the y-values are 1, 2, 3, 4, and 5. These are just to space out the categories. A line graph is also possible for vertical orientation. You add data markers to your dots and make the line connecting them invisible.
It is not easy to create the connected dots plot using a tool that doesn’t have built-in functionality. However, it is possible. It will usually be a combination of line graphs and scatterplots for connecting dots. A stacked bar chart is used for the connection. The following step-by-step guide will show you how to create a connected dot plot using Excel.
There are many ways to draw a dot plot but the best way to begin is to draw it by hand.
Step 1 Choose a scale to set it up.
We will create a horizontal scale. All values must be enclosed. For this data set, the smallest value is 0. The largest value is 9. The number line number books will give the title.
Step 2 – Plot the dots.
This step will require you to fill in the dots with your scale. Remember that each value is assigned a dot and the dots are stacked. Let’s plot only the first row. This will help us verify this. Each value is represented by a dot in the plot. We can now continue with the operation once we have all the details. While you won’t be able to do it perfectly by hand, you can make sure the dots match up. Broad gaps between dots should not make one value appear more predominant than the other.
And that’s it! Because it is easy to create and read, they are excellent for data representation, especially when making dot plots in Excel.
Pros and cons of Dot Plots
Dots in a plot are lighter than the common bar chart. This is because they use less ink. The connected and Cleveland dot plots offer additional freedom. Instead of starting at zero, the axis can start at any point.
Dot plots, however, aren’t as common as bars. This may be a positive in some cases. They may not be accepted by people who are unfamiliar with the situation.
Important Notes:
Take a look at these important notes!
- It depicts the distribution of numerical variables, where a value can be represented by each dot on either a graph or a number line.
- The Wilkinson dot diagram shows the distribution of continuous data points such as a histogram. It displays individual data points instead of bins.
- The Cleveland dot plot displays graphic data elements and a continuous variable as opposed to a categorical.
Summary
A Dot Plot, in summary, is a graph that shows the distribution of the qualitative variable. Each dot represents an individual value. If a whole number is more than one value, the dots are placed above each other so that the height in the column represents the frequency of that value.
Note Dot plots don’t look the same as Scatterplots. They are more like a histogram because it sorts data into BINs. With software such as SPSS, you can create dot charts.
