The goal of this study is to better understand how methods for estimating treatment effects of latent groups operate. In particular, the authors identify where violations of assumptions can lead to biased estimates, and explore how covariates can be critical in the estimation process. For each set of approaches, the authors first review the…

To date, evaluation research and policy analysis have focused mainly on average program impacts and paid little systematic attention to their variation. Recently, the growing number of multi-site randomized trials that are being planned and conducted make it increasingly feasible to study "cross-site" variation in impacts. Important…

This "What Works Clearinghouse Procedures and Standards Handbook (Version 3.0)" provides a detailed description of the standards and procedures of the What Works Clearinghouse (WWC). The remaining chapters of this Handbook are organized to take the reader through the basic steps that the WWC uses to develop a review protocol, identify…

Education researchers, practitioners, and policymakers alike are committed to identifying interventions that teach students more effectively. Increased emphasis on evaluation and accountability has increased desire for sound evaluations of these interventions; and at the same time, school-level data have become increasingly available. This article…

The statistical methods presented in this workbook focus on the display of central tendency, statistical tests, and correlation. Chapters 2, 3, and 4 consist of worksheets, each of which provides step-by-step instructions for calculating and interpreting a particular statistical method. The introduction to each worksheet explains how and when to…

The study reported here provides a theoretical and empirical framework for the analysis of employment tax credit policy (a government subsidy or business tax credit to firms who maintain or expand their use of labor). Various programs are examined from the standpoint of structure and implications. The programs are selective employment incentive;…