Principles and Practice
Calls for rigorous impact evaluation have been accompanied by the quest not just to find out what works but why. It is widely accepted that a theory-based approach, one that maps out the causal chain from inputs to outcomes and impact and tests the underlying assumptions, will shed light on the 'why' question. But application of a theory-based approach remains weak. This paper identifies six principles to successful application of the approach:
- map out the causal chain (programme theory);
- understand context;
- anticipate heterogeneity;
- rigorously evaluate impact using a credible counterfactual;
- conduct rigorous factual analysis; and
- use mixed methods.
