Randomized controlled trials (RCTs) and regression discontinuity (RD) studies both provide estimates of causal effects. A major difference between the two is that RD only estimates local average treatment effects (LATE) near the cutoff point of the forcing variable. This has been cited as a drawback to RD designs (Cook & Wong, 2008).…

As a result of the 1998 reauthorization of Head Start, the Department of Health and Human Services conducted a national evaluation of the Head Start program. The goal of Head Start is to improve the school readiness skills of low-income children in the United States. There is a substantial body of experimental and correlational research that has…

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…

An examination of the scientific basis of both control group designs and comparative designs in outcome research reveals that comparative designs generally have fewer threats to validity and provide a more efficient means of control for nonspecific treatment factors suggesting that comparative studies warrant a larger role in the study of…

Criteria for suitable research designs for use with large databases are suggested and analyzed. The advantages and disadvantages of several types of quasi-experimental designs are compared. Examples are taken from the authors' research with data from the Manitoba Health Services Commission. (Author/AL)

This article discusses research design problems peculiar to work with intellectually disabled subjects, such as discrepancies in uses of control groups and mental age matching, definitions of subject groups and variability within and between subject groups. Suggestions for minimizing these problems are made and alternative methodologies offered.…

The problem of the appropriate comparison group for bereavement studies is discussed. The use of the retrospective pretest design is illustrated through a longitudinal study of bereavement outcome following pregnancy loss, involving 138 bereaved women and a comparison group of 215 currently pregnant women. (SLD)

Evidence is presented that strengthens the argument against comparison group research strategies. Results from a study of youth attitudes related to the California Conservation Corps involving 528 participants and 668 comparisons indicate that the comparison group may not adequately represent the nontreatment state. (SLD)

In policy research a frequent aim is to estimate treatment effects separately by subgroups. This endeavor becomes a methodological challenge when the subgroups are defined by post-treatment, rather than pre-treatment, variables because if analyses are performed in the same way as with pre-treatment variables, causal interpretations are no longer…

Research efforts have established that the Mantel-Haenszel procedure (MHP) is an effective method for detecting the presence of test items exhibiting differential item functioning (DIF). While the MHP has been advocated for situations where item response theory based methods may not be usable, recent findings have suggested that the performance of…

The New York State Experimental Prekindergarten Program (PreK) evaluation studied successive waves of children while they were in PreK, and as they progressed through the third grade. For each wave, two control groups were obtained: (1) A waiting-list control group, children in districts offering PreK programs who were identified as eligible for…