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Berk Ozler's blog

Beware of studies with a small number of clusters

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While some of us get to conduct individually randomized trials, I’d say that cluster randomized trials are pretty much the norm in field experiments in economics. Add to that the increase in the level of ambition we recently acquired to have interventions with multiple treatment arms (rather than one treatment and one control group) and mix it with a pinch of logistical and budgetary constraints, we have a non-negligible number of trials with small numbers of clusters (schools, clinics, villages, etc.).

A second Industrial Revolution, replication worries, yawns, and more…

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I made a temporary move recently, which left me without a dog walker for our two beloved (and very active) dogs, without a delivery option for good takeout food, and a need to build a fire in a wood stove every day. I had never spent this much time during weekdays walking the dogs, cooking, and carrying wood from the garage to build and maintain a fire throughout the day. Without the takeout food and all the hiking, I am healthier and somewhat less stressed, but the shift in time use takes some adjusting to…

Making small gains loom large: A review of Rosenzweig’s review of Poor Economics

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Suppose that you’re told that a program reduced the rate of dropping out of school among 15 year-olds by 17% and this reduction was statistically significant. You are also told that the same figure among 12 year-olds is 38%. You would likely take note. Suppose now you’re told that these are the effects of a conditional cash transfer program, where the dropout rate among the control group is 37.7% and 16.8%, respectively for ages 15 and 12, thus the absolute effect sizes are 6.4 percentage points in each case.

Mind Your Cowpeas and Cues: Inference and External Validity in RCTs

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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 different seeds of cowpeas to farmers in Tanzania.

When Randomization Goes Wrong...

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An important, and stressful, part of the job when conducting studies in the field is managing the number of things that do not go according to plan. Markus, in his series of field notes, has written about these (see, for example, here and here) roller coaster rides we call impact evaluations.

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