The data are for an area of Arahazar upazila, Bangladesh.
The researchers labelled each well with its level of arsenic and an
indication of whether the well was ``safe'' or ``unsafe.'' Those using unsafe
wells were encouraged to switch. After several years, it was determined
whether each household using an unsafe well had changed its well.
These data are used by Gelman and Hill (2007) for a logistic-regression example.
References
A. Gelman and J. Hill (2007)
Data Analysis Using Regression and Multilevel/Hierarchical Models.
Cambridge: Cambridge University Press.