Can a single case be used to test theory?

This post is by Richard Nielsen on the Social Science Statistics Blog, hosted by the Institute for Quantitative Science at Harvard University.

Every so often, I try to take some time to read something that I should have read ages ago. Tonight’s gem was the 2010 draft of “The Industrial Organization of Rebellion: The Logic of Forced Labor and Child Soldiering” by Bernd Beber and Chris Blattman (link). The paper gets a lot of traction out of a formal model and then matches these predictions up to reality using some unique and hard-earned data.

An off-hand comment in the paper caught my attention: Beber and Blattman’s assertion that “a single case helps to refine our theory and validate some basic assumptions, but cannot test it” (p 19). Ordinarily I’d say “sure”, except that they are referring to their own nuanced analysis of a large number of child soldiers painstakingly tracked down in Uganda. Moreover, they actually have a credible identification strategy — abduction into the Lord’s Resistance Army was essentially random after conditioning on age and location. I was pretty convinced by the analysis; more so than by the regressions on the novel but dubious rebel dataset they introduce at the end of the paper. Maybe the Uganda child-soldier analysis wasn’t a “test” but it sure moved my posterior beliefs about their hypotheses…

Read the full blog-post here.