3ie ~ International Initiative for Impact Evaluation

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Working Paper 15

Addressing attribution of cause and effect in small n impact evaluations: towards an integrated framework

June 2012

There exists considerable consensus among impact evaluators conducting large n impact evaluations involving tests of statistical difference in outcomes between the treatment group and a properly constructed comparison group. However no such consensus exists when it comes to assessing attribution in small n cases – that is when there are insufficient units of assignment to conduct statistical analysis of what difference the intervention has made. Howard White and Daniel Phillips examine various evaluation approaches that could potentially be suitable for small n analysis and find that a number of them share a methodological core which could provide a basis for consensus.

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