The MRC has had advice on evaluating “complex interventions” since 2000, updated 2008. By complex interventions, they mean things like encouraging children to walk to school, not complex in the sense of being made up of many parts, but complex in the sense that the way it happens and the effect it has is hard to predict because of non-linearities, interactions and feedback loops. Complexity is something I have been thinking and reading about a lot recently; it really is unavoidable in most of the work I do (I never do simple RCTs; I mean how boring is it if your life’s work is comparing drug X to placebo using a t-test?) and although it is supertrendy and a lot of nonsense is said about it, there is some wisdom out there too. However, I always found the 2000/8 guidance facile: engage stakeholders, close the loop, take forward best practice. You know you’re not in for a treat when you see a diagram like this:
Now, there is a new guidance document out that gets into the practical details and the philosophical underpinnings at the same time: wonderful! There’s a neat summary in the BMJ.
What I particularly like about this, and why it should be widely read, is that it urges all of us researchers to be explicit a priori about our beliefs and mental causal models. You can’t measure everything in a complex system, so you have to reduce it to the stuff you think matters, and you’d better be able to justify or at least be clear about that reduction. It acknowledges the role that context plays in affecting the results observed and also the inferences you choose to make. And it stresses that the only decent way of finding out what’s going on is to do both quantitative and qualitative data collection. That last part is interesting because it argues against the current fashion for gleeful retrospective analysis of big data. Without talking to people who were there, you know nothing.
My social worker colleague Rick Hood and I are putting together a paper on this subject of inference in complex systems. First I’ll be talking about it in Rome at IWcee (do come! Rome is lovely in May), picking up ideas from economists, and then we’ll write it up over the summer. I’ll keep you posted.