A rant on the external validity double double-standard
Concerns about external validity are a common critique of micro work in development, especially experimental work. While not denying that it is useful to learn what works in a variety of different...
View ArticleIt worked for you. Will it work for me?
Following on David’s rant on external validity yesterday, which turned out to be quite popular, I decided to keep the thread going. Despite the fact that the debate is painted in ‘either/or’ terms, my...
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Teachers don’t matter says Nobel Laureate: A new study in Science, and why...
At a recent seminar someone joked that the effect size in any education intervention is always 0.1 standard deviations, regardless of what the intervention actually is. So a new study published last...
View ArticleMoving from Internal to External Validity – and problems with Partner...
When done well, randomized experiments at least provide internal validity – they tell us the average impact of a particular intervention in a particular location with a particular sample at a...
View ArticleWhat the HIV prevention gel trial failure implies for trials in economics
For the World AIDS Day, there is a sign at the World Bank that states that taking ARVs reduces rate of HIV transmission by 96%. If this was last year, a sign somewhere may well have read “A cheap...
View ArticleWEIRD samples and external validity
A core concern for any impact evaluation is the degree to which its findings can be generalized to other settings and contexts, i.e. its “external validity”. But of course external validity concerns...
View ArticleMind Your Cowpeas and Cues: Inference and External Validity in RCTs
There is a minor buzz this week in Twitter and the development economics blogosphere about a paper (posted on the CSAE 2012 Conference website) that discusses a double blind experiment of providing...
View ArticleWeighting for external validity, then waiting for election results
Well I’m writing this on Election Day evening here in the U.S., and am rather consumed by the events at hand. Like many of our readers I have been following various poll aggregators (here, here, and...
View ArticleThinking about the placebo effect as a “meaning response” and the implication...
In recent conversations on research, I’ve noticed that we often get confused when discussing the placebo effect. The mere fact of positive change in a control group administered a placebo does not...
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