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power calculations

Power calculations: what software should I use?

Berk Ozler's picture

In my experimental work, I almost always do cluster-randomized field experiments (CRTs – T for trials), and therefore I always used the Optimal Design software (OD for short), which is freely available and fairly easy to use with menu based dialogue boxes, graphs, etc. However, preparing some materials for a course with a couple of colleagues, I came to realize that it has some strange basic limitations. That led me to invest some time into finding out about my alternatives in Stata. I thought I’d share a couple of things I learned here.

Notes from the AEAs: Present bias 20 years on + Should we give up on S.D.s for Effect Size?

David McKenzie's picture
I just got back from the annual meetings of the American Economic Association (AEAs) in Boston. It’s been a couple of years since I last went, and after usually going to just development conferences, it was interesting to see some of the work going on in other fields. Here are a few notes:

gender power doesn't come cheap

Markus Goldstein's picture

coauthored with Alaka Holla

As we argued last week, we need more results that tell us what works and what does not for economically empowering women. And a first step would be for people who are running evaluations out there to run a regression that interacts gender with treatment.   Now some of these will show no significant differences by sex.   Does that mean that the program did not affect men and women differently? No. Alas, all zeroes are not created equal.  

Power Calculations 101: Dealing with Incomplete Take-up

David McKenzie's picture

A key issue in any impact evaluation is take-up (i.e. the proportion of people offered a program who use it). This is particularly an issue in many finance and private sector (FPD) programs. In many health and education programs such as vaccination campaigns or getting children to school programs, the goal of the program is actually to have all eligible individuals participate. In contrast, universal take-up is not the goal of most FPD programs, and, even when it is a goal, it is seldom the reality.

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.