ABSTRACT
You are told: use policies that work. And you are told: RCT’s – randomized controlled trials – will show you what these are. That’s not so. RCT’s are great, but they do not do that for you. They cannot alone support the expectation that a policy will work for you. What they tell you is true – that this policy produced that result there. But they do not tell you why that is relevant to what you need to bet on getting the results you want here. For that, you will need to know a lot more.
