One of the things I get asked when people are designing experiments – when they are either interested in or worried about spillover effects – is how to divvy up the clusters into treatment and control and what share of individuals within treatment clusters to assign within-cluster controls. The answer seems straightforward – it may look intuitive to assign a third to each group and I have seen a few designs that have done this, but it turns out that it’s a bit more complicated than that. There was no software that I am aware of that helped you with such power calculations, until now...
On May 25, I attended a workshop organized by the Harvard School of Public Health, titled “Causal Inference with Highly Dependent Data in Communicable Diseases Research.” I got to meet many of the “who’s who” of this literature from the fields of biostatistics, public health, and political science, among whom was Elizabeth Halloran, who co-authored this paper with Michael Hudgens – one of the more influential papers in the field.
Pardon the pun. But, psychological wellbeing has been in the news recently: do cash transfer programs have negative spillover effects on those who live near beneficiaries but do not receive transfers themselves?