In paired experiments, participants are grouped into pairs with similar characteristics, and one observation from each pair is randomly assigned to treatment. The resulting treatment and control groups should be well-balanced; however, there may still be small chance imbalances. Building on work for completely randomized experiments, we propose a…

As a result of the use of random assignment to treatment, randomized experiments typically have high internal validity. However, units are very rarely randomly selected from a well-defined population of interest into an experiment; this results in low external validity. Under nonrandom sampling, this means that the estimate of the sample average…

Recent research on the design of social experiments has highlighted the effects of different design choices on research findings. Since experiments rarely collect their samples using random selection, in order to address these external validity problems and design choices, recent research has focused on two areas. The first area is on methods for…