Dummy Coding and Effect Coding in Regression Models Webinar

by Karen


Sooner or later, every researcher needs to include categorical predictors in a regression model. There are different coding schemes that make it possible to interpret the coefficients of these categorical predictors. This webinar will explain and compare two of the most popular: dummy coding and effect coding.

In one hour you will learn:

  • the difference between dummy coding and effect coding
  • how to do each for both binary and multicategory predictors
  • how to interpret the regression coefficients in both coding schemes
  • why it’s important to be able to use both

We’ll run through an example or two to show how the same information is presented in different ways under the two coding schemes, and how ANOVA, which uses effect coding, and regression, which uses dummy coding, are really two sides of the same coin.

This webinar has already taken place, but you can get the recording here.


What’s a The Craft of Statistical Analysis Webinar?  It’s a regular webinar series for researchers to help you hone the craft of statistical analysis.  Each webinar is about a single statistical topic that is often confusing, misunderstood, or not well known to researchers.  Check it out and pass the word along–they’re free!
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{ 3 comments… read them below or add one }

A Memon


I have a specific question about the effect coding. I can understand when only one reference category is missing so we code that as -1. In my model I have 5 road classses and 5 vehcile classes. When I am using regreesion I usually miss intentionally (drop) one category from road class and one cetgory from vehcile class which are coded as -1. The problem arises when I am coding interaction (4X4) in my main model. How to code -1 in interactions and which one. Do i have to code all 8 groups (interactions) as -1 for which I am dropping the main variables.


Ibrahim E

Dear Sir/Madam:
I am trying to learn ‘dummy coding’. Is there any possibility to reach “Webinar Announcement: Dummy Coding and Effect Coding in Regression Models”s one hour video ?
If you help me to reach very appreciated.
Best Regards,
Ibrahim E. Bilici
Erciyes University School of Communications.



Hi Ibrahim–we’re working on editing it. But there is much more on dummy coding in my Interpreting Regression Coefficients workshop–it’s over, but you can get the transcript. It goes into much more detail, including binary and multi-category predictors with interactions.


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