This article reviews the origins and use of the terms quasi-experiment and natural experiment. It demonstrates how the terms conflate whether variation in the independent variable of interest falls short of random with whether researchers find, rather than intervene to create, that variation. Using the lens of assignment--the process driving…

Until now, the conventional approach using two distinct groups, experimental and control, continues to dominate research, especially education research. Researchers, particularly those who are active in this domain, readily recognise this pattern when surveying literature. This article explores the use of the Solomon four-group design as a…

Scholarly efforts to identify core design features for effective teacher professional development have grown rapidly in the last 25 years. Many concise lists of design principles have emerged, most of which converge on a consensus of 5-7 presumably 'effective' features (e.g. collaborative tasks, active learning, focus on content). The…

The randomized control trial (RCT) is the primary experimental design in education research due to its strong internal validity for causal inference. However, in situations where RCTs are not feasible or ethical, quasi-experiments are alternatives to establish causal inference. This paper serves as an introduction to several quasi-experimental…

The enormous developments in technology and hence the widespread use of hand-held devices in the last few decades have led to great interest in mobile-assisted language learning (MALL) as a new way of language education. MALL is considered an effective method particularly for young language learners due to their higher level of familiarity with…

Randomized control trials are considered the pinnacle for causal inference. In many cases, however, randomization of participants in social work research studies is not feasible or ethical. This paper introduces the co-twin control design study as an alternative quasi-experimental design to provide evidence of causal mechanisms when randomization…

To date, there has been mounting research evidence on the impact of written corrective feedback. In response to this, reviews have been conducted to condense either findings or methodologies through the combined analysis of EFL and ESL studies. Although syntheses shed light on the topic, no one provides exclusive insights into EFL realities.…

The What Works Clearinghouse (WWC) identifies existing research on educational interventions, assesses the quality of the research, and summarizes and disseminates the evidence from studies that meet WWC standards. The WWC aims to provide enough information so educators can use the research to make informed decisions in their settings. This…

Education decisionmakers need access to the best evidence about the effectiveness of education interventions, including practices, products, programs, and policies. It can be difficult, time consuming, and costly to access and draw conclusions from relevant studies about the effectiveness of interventions. The What Works Clearinghouse (WWC)…

This paper introduces a simple, quotient effect size, termed (for 'quotient'), suitable for reporting on the effectiveness of educational interventions. The quotient effect size for a pre-test-post-test design is defined as the gain score (i.e. post-test minus pre-test) for the intervention group, divided by the gain score for the control group.…

The distribution of the standardized mean difference is well understood. However, in many situations, researchers need to estimate an effect size to represent the relationship between a continuous outcome and a dichotomous grouping variable, adjusting for the effect of a covariate (or a set of covariates). Typically, this adjustment takes place…

Group design research studies can provide evidence to draw conclusions about "what works," "for whom," and "under what conditions" in special education. The quality indicators introduced by Gersten and colleagues (2005) have contributed to increased rigor in group design research, which has provided substantial…

The What Works Clearinghouse (WWC) systematic review process is the basis of many of its products, enabling the WWC to use consistent, objective, and transparent standards and procedures in its reviews, while also ensuring comprehensive coverage of the relevant literature. The WWC systematic review process consists of five steps: (1) Developing…

Interrupted time series (ITS) studies are frequently used to examine the impact of population-level interventions or exposures. Systematic reviews with meta-analyses including ITS designs may inform public health and policy decision-making. Re-analysis of ITS may be required for inclusion in meta-analysis. While publications of ITS rarely provide…

Background: Special education services are individualized supports provided to students with disabilities (SWD) that should help them make appropriate educational progress given their abilities, educational needs, and goals (Endrew F. v. Douglas County School District, 2017). Concerns about the benefits of these services have emerged given the…