In this paper, we examine the validity and precision of two nonexperimental study designs (NXDs) that can be used in educational evaluation: the comparative interrupted time series (CITS) design and the difference-in-difference (DD) design. In a CITS design, program impacts are evaluated by looking at whether the treatment group deviates from its…

Matching, randomization, random sampling, and other methods of controlling extraneous variation are discussed. The purpose was to specify the benefits of randomization in estimating causal effects of treatments. It is concluded that randomization should be employed whenever possible, but the use of carefully controlled nonrandomized data to…

This self-contained and self-instructional unit is intended for use by evaluation and development personnel and by students in introductory research and evaluation courses. The unit contains a discussion of the regression employing graphic illustrations with actual data. The user is introduced to the regression effect in the single group…

The purpose of this study was to compare the results of an analysis of covariance design to a method developed by the authors called within-class regression. Application of this statistical method can be to any quasiexperimental design with a large number of groups. A test of statistical significance to use with the within-class regression…

The National Job Corps Study was conducted in 1994-1996 to provide a thorough and rigorous assessment of the impacts of the Job Corps on key participant outcomes. To ensure that the study was well implemented, a study team from Mathematica Policy Research, Inc., (MPR) investigated outcome and admission (OA) procedures in each Job Corps region and…