The Effect: An Introduction to Research Design and Causality

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Welcome to the web version of The Effect. The Effect will soon be out in published form from Chapman & Hall, but they have allowed this free Bookdown version to remain here on This Bookdown version will continue to be free, but I also hope that you will purchase the published version when it is available. If you would like to be kept informed about updates to the book, such as when the published version is available for preorder but also other updates, please add your email to the mailing list (no more than one email/month).

The Effect is a book intended to introduce students (and non-students) to the concepts of research design and causality in the context of observational data. The book is written in an intuitive and approachable way and doesn’t overload on technical detail. Why teach regression and research design at the same time when they are fundamentally different things? First learn why you want to structure a design in a certain way, and what it is you want to do to the data, and then afterwards learn the technical details of how to run the appropriate model.

This book consists of a Part 1 dedicated to research design and causality, making use of causal diagrams to make the concept of identification straightforward, and a Part 2 dedicated to implementation and common research designs like regresson with controls and regression discontinuity. You can see the chapters and navigate between them on the left (on in the dropdown menu up top if you’re on a small screen).

If you would like to run the code examples in this book, you’ll need the causaldata package, which contains the example data for most of the code chunks. Causaldata can be installed using install.packages('causaldata') in R, ssc install causaldata in Stata, or pip install causaldata in Python.

0.1 Revision and Updates

This book is still in the revision process. Please do send any comments or questions about the material to or to me on Twitter at nickchk. You can also submit feedback, or report any typos or formatting errors you find, in the Feedback Form.

Things that should be coming relatively soon:

  • Additional edits in preparation for the final publication draft.
  • A search bar to easily search through all the chapters in the book.
  • Chapter-heading illustrations.
  • A new series of videos (adding to my library of them) designed to accompany the book.
  • Homework assignment sets for instructors to use when they use the book to teach.

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