Isn’t the problem you’re raising here simply that the studies tend to look at populations rather than individuals or even sub-groups? It’s a neat way to demonst

Isn’t the problem you’re raising here simply that the studies tend to look at populations rather than individuals or even sub-groups? It’s a neat way to demonstrate the problem. The challenge is that as long as we treat the RCT as the primary means by which we build knowledge, it will remain difficult to study sub-groups because it’s so hard to obtain a sufficient sample.