Field note · April 17, 2024
Cutting a lesson down — Correlation, confounding, and Simpson's paradox
The gap between "these move together" and "this causes that" is where most bad decisions live. Here is how to see the gap, and what to do when you cannot close it.
A note from writing Correlation, confounding, and Simpson's paradox, which took three passes to get to something short.
The gap between "these move together" and "this causes that" is where most bad decisions live. Here is how to see the gap, and what to do when you cannot close it.
The hard part of writing this was cutting it. The first version covered every case; the useful version covers the case you hit on a Tuesday and names the rest in a sentence. Completeness is a property of reference material, not of teaching material, and confusing the two produces something nobody finishes.
It sits in the Statistics you will actually use module, and the exercise runs against world-indicators. That pairing is deliberate: the dataset was built with the trap the lesson describes already in it, so the exercise fails in the instructive way rather than the confusing one.
Ordering matters here more than in most courses. It follows The five tests that cover most questions and leads into Designing an experiment that can succeed, and reading it out of sequence mostly works but costs you the setup.
Free means free, and it also means we can rewrite it whenever it is wrong. No edition, no errata PDF, nothing to repurchase. The whole course is 36 lessons and the fixes land the day we find them.