David Evans' personal blog

A few months ago I read this paper on how to do randomization; it has just come on-line, and I recommend it highly. Meanwhile, I summarized it; here are the greatest hits.In Pursuit of Balance: Randomization in Practice in Development Field Experiments
By Miriam Bruhn (WB) and David McKenzie (WB, IZA, BREAD)

The plan:

Randomized experiments are increasingly used in development economics. … This paper carries out an extensive review of the randomization methods used in existing randomized experiments, presents new evidence from a survey of leading development economists, and carries out simulation results in order to provide guidance for researchers considering which method to use for randomization.

The shortest summary of results:

in samples of 300 or greater, the different randomization methods perform similarly in terms of achieving balance in outcomes variables at follow-up. In smaller samples, however, the choice of randomization method is important, with matching and stratification performing best at achieving balance. Moreover, the ex-post analysis should explicitly account for how the randomization was conducted by including the appropriate controls. [Don’t worry: they tell us how!]

Continue reading “okay, i’ll randomize; but how should i do it?” →

Across the African countries I have worked in, I have been surprised at the high rates of grade repetition. In the United States, grade repetition is relatively rare (in my experience) whereas in Kenya almost every child I knew had repeated at least one grade.

Three researchers shed some light on the topic in a new working paper: Promotion with and without Learning: Effects on Student Enrollment and Dropout Behavior. They provide the arguments for both high grade repetition and low, a literature review, and some new research. Here’s the new stuff.

This study examines a different aspect of the debate about grade retention and promotion. In particular, we explicitly consider how parents process the information that grade promotion or retention provides about student achievement and integrate that information into parental decisions regarding their children’s schooling.4 In developing countries, even at the earliest grades, parents implicitly evaluate whether the value of their schooling dominates the opportunity costs of child time outside of school, and these assessments may be influenced by whether the child is perceived to be learning from school.

And the findings

Even more striking, largely illiterate parents appear to base their decisions of whether to send the child to school for another year largely on merit-based promotions. Promotions that are not correlated with measured student cognitive attainments have a much smaller positive impact on the probability of school continuation. This finding implies that parents make their decisions regarding a child’s continued schooling on the basis of perceived learning in the previous year, rather than on promotion or repetition per se. It would also suggest that if a child’s ability to learn in future years is reduced by being placed in a grade for which the child is unprepared, then promotion could lead to increased dropout.

More below

Continue reading “repeat a grade or just drop out?” →