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Effect size

What is success, anyhow?

Markus Goldstein's picture

As a fair number of impact evaluations I work on are programs designed by governments or NGOs, I often initially have to have a tricky discussion when it comes time to do the power calculations to design the impact evaluation.   The subject of this conversation is the anticipated effect size.   This is a key parameter – if it’s too optimistic you run the risk of an impact evaluation with no effect even when the program had worked to some (lesser) degree, if it’s too pessimistic, then you are wasting money and people’s time in your survey.