Reflections on Methodology

MDRC is well known as a leader in advancing rigorous research methods in program improvement and evaluation and in sharing what we learn with the field. With the launch of Reflections on Methodology, Kristin Porter presents posts by MDRC researchers and colleagues on the refinement and practical use of cutting-edge research methods being employed across our organization.

Porter, a Senior Associate at MDRC, is currently contributing to MDRC’s work in predictive analytics, multiple hypothesis testing, regression discontinuity designs, and heterogeneity of impacts in randomized controlled trials. She holds a PhD in biostatistics from the University of California, Berkeley. 

12/2018 | Meghan McCormick, Michelle Maier

Social and education policy researchers often work in partnership with the practitioners who develop and implement the programs being studied. Engagement with those who design and use a program is particularly helpful in developing measures of implementation fidelity — that is, whether a program is being implemented as designed. There are two goals here: Researchers want to understand why an intervention did or did not produce effects, and practitioners want to use the information to make improvements beyond the study period.

11/2018 | Dan Bloom

Andrew Leigh’s irresistibly readable new book Randomistas takes readers on a rollicking tour of disciplines in which randomized controlled trials (RCTs) have revolutionized the way we build knowledge. From medicine to social policy to crime control, RCTs have helped to debunk myths and improve the lives of millions. We were proud to see that MDRC, and its former president Judith Gueron, figure prominently in the chapter on “Pioneers of Randomisation.” Leigh takes on — and mostly demolishes — the most commonly repeated myths about random assignment.

10/2018 | Charles Michalopoulos

Social policy evaluations usually draw inferences using classical statistical methods (also known as frequentist inference). An evaluator may, for example, compare outcomes for program and control groups and make statements about whether estimates are statistically significant. This approach has two important shortcomings, which Bayesian analysis can address.

07/2018 | Rebecca Unterman

A previous post described how school enrollment processes that contain naturally occurring lotteries provide researchers with exciting opportunities to learn about the effects of policies and programs. This follow-up post presents a few methodological issues common to lottery-based analyses — constrained statistical power, imperfect compliance, and restricted generalizability — and briefly discusses how they can be addressed.

05/2018 | Shira Kolnik Mattera, Marie-Andrée Somers

A two-stage, multilevel approach to random assignment is an intriguing way to test a complex set of interventions — such as interventions children experience in sequence as they move from preschool to kindergarten. In the first stage of such a design, groups (schools or centers) of participants are randomly assigned to program and control groups. In the second stage, individuals within those groups (students or children) are randomized to two different conditions. This design creates up to four groups — a group that receives both interventions, a group that receives the first intervention but not the second, a group that receives the second intervention but not the first, and a control group. By comparing the outcomes of participants in these groups, the combined and relative effects of the two interventions can be tested.

04/2018 | Howard Bloom, Michael J. Weiss

In a recently published three-article set, MDRC researchers and colleagues discuss quantifying cross-site impact variation using data from multisite randomized trials. The papers show that the extent to which the effects of an intervention vary across settings has important implications for policy, practice, science, and research design. This post distills some key considerations for research design and for reporting and interpreting cross-site impact variation.

03/2018 | Stephen Nuñez, Audrey Yu

Community initiatives that aim to make neighborhoods safer, improve schools, and preserve affordable housing have long emphasized the importance of building good relationships between participating organizations. To understand how the structure of such relationships contributed to outcomes in one such initiative, MDRC applied the methodology of social network analysis to data from a survey administered to organizations in nine Chicago neighborhoods.

02/2018 | Rebecca Unterman

Researchers across disciplines have long taken advantage of natural experiments to study the effects of policies at full scale. In the past decade rapid growth in the number of charter schools and school district choice systems has provided education researchers with exciting opportunities to do the same: to use naturally occurring pockets of randomization to rigorously study the effects of policy-relevant education reforms that are already in place, often on a large scale.


01/2018 | Rachel Rosen

Many researchers are concerned about a crisis in the credibility of social science research because of insufficient replicability and transparency in randomized controlled trials and in other kinds of studies. In this post we discuss some of the ways that MDRC strives to address these issues and ensure the rigor of its work.

11/2017 | Kristin Porter

Researchers are often interested in testing the effectiveness of an intervention on multiple outcomes, for multiple subgroups, at multiple points in time, or across multiple treatment groups. The resulting multiplicity of statistical hypothesis tests can increase the likelihood of spurious findings: that is, finding statistically significant effects that do not in fact exist. Without the use of a multiple testing procedure (MTP) to counteract this problem, the probability of false positive findings increases, sometimes dramatically, with the number of tests. Yet the use of an MTP can result in a substantial change in statistical power, greatly reducing the probability of detecting effects when they do exist.

10/2017 | Kelsey Schaberg, Richard Hendra

The Subprime Lending Data Exploration Project is a “big data” project designed to produce policy-relevant insights using an administrative data set that covers nearly 50 million individuals who have applied for or used subprime credit. The data set contains information on borrower demographics, loan types and terms, account types and balances, and repayment histories. To investigate whether there were distinct groups of borrowers in terms of loan usage patterns and outcomes, we used a data discovery process called K-means clustering.

09/2017 | Kristin Porter, Rekha Balu, Richard Hendra

Across policy domains, practitioners and researchers are benefiting from a trend of greater access to both more detailed and frequent data and the increased computing power needed to work with large, longitudinal data sets. There is growing interest in using such data as a case management tool, to better understand patterns of behavior, better manage caseload dynamics, and better target individuals for interventions. In particular, predictive analytics — which has long been used in business and marketing research — is gaining currency as a way for social service providers to identify individuals who are at risk of adverse outcomes. MDRC has multiple predictive analytics efforts under way, which we summarize here while highlighting our methodological approach.