Evaluating blocked randomized experiments from a potential outcomes perspective has two primary branches of work. The first focuses on larger blocks, with multiple treatment and control units in each block. The second focuses on matched pairs, with a single treatment and control unit in each block. These literatures not only provide different…

Hierarchical models are extremely promising tools for data analysis, but it is important not to lessen hard thinking about data and iterative model checking when fitting hierarchical models. More and better software, methods to assure proper calibration, and materials in support of hierarchical model use are all needed. (SLD)