Cutting a lesson down — Causal claims when you cannot randomise

A note from writing Causal claims when you cannot randomise, which took three passes to get to something short.

Half the interesting questions cannot be tested. Here is what is available instead, what each method assumes, and how to state a conclusion you can defend.

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 Experiments and causal claims module. The exercise is a thinking one rather than a query one — some of this material is about deciding what to compute, and that does not need a keyboard.

Ordering matters here more than in most courses. It follows Reading a result without fooling yourself and leads into Frame the problem, then beat a stupid baseline, 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.