This discussion is incredibly helpful. @HuwLlewelyn joins @Stephen Senn in being the most impressive scientists I’ve known in their abilities to cut through arguments of others and to make cogent new arguments. It confirms what @Stephen has argued repeatedly that principles of experimental and clinical trial design must be brought to causal inference about treatment effects. The discussion also confirms my previous feeling that outside of special situations (such as analysis of treatment effects within RCTs compensating for non-adherence to treatment) causal inference remains a theoretical nicety and a great thought organizer but has not yet been translated to practical application in treatment evaluation. Hence the lack of uptake on the challenge put at https://discourse.datamethods.org/t/examples-of-solid-causal-inferences-from-purely-observational-data.
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