Reference: https://doi.org/10.1093/aje/kwi067

In selecting the community for this Colford study, the authors had to balance diverse and somewhat conflicting objectives. Some of the selection criteria pertain to the cooperativeness of the water utility and availability of monitoring data. Others were presumably intended to increase the power of the study to detect an effect of water filters, whereas others were presumably intended to make the results more generalizable. What is an example of a selection criterion intended to increase the generalizability of the results of this study?