Background: The generalizability of a study's results continues to be at the forefront of concerns in evaluation research in education (Tipton & Olsen, 2018). Over the past decade, statisticians have developed methods, mainly based on propensity scores, to improve generalizations in the absence of random sampling (Stuart et al., 2011; Tipton,…

Experimental studies of educational interventions are rarely based on representative samples of the target population. This simulation study tests two formal sampling strategies for selecting districts and schools from within strata when they may not agree to participate if selected: (1) balanced selection of the most typical district or school…

For decades, the notion of teachers engaging in research has been discussed and carried out under the heuristics and methodologies of action research (Manfra, 2019; Pine, 2009). A typical action research project might involve an individual teacher studying the effectiveness of a specific instructional strategy like having students preview content…

Questions regarding the generalizability of results from educational experiments have been at the forefront of methods development over the past five years. This work has focused on methods for estimating the effect of an intervention in a well-defined inference population (e.g., Tipton, 2013; O'Muircheartaigh and Hedges, 2014); methods for…

Background: Educational researchers have long espoused the virtues of writing with regard to student cognitive skills. However, research on the reliability of the grades assigned to written papers reveals a high degree of contradiction, with some researchers concluding that the grades assigned are very reliable whereas others suggesting that they…

A structural equation modeling approach to scale reliability evaluation can be employed to estimate generalizability theory indexes in settings where sampling of subjects and conditions is carried out. In one- and two-facet crossed designs, it is demonstrated how this method can be used to obtain estimates of relative generalizability…

The zeitgeist for reform in education precipitated a number of changes in assessment. Among these are performance assessments, sometimes linked to "high stakes" accountability decisions. In some instances, the trustworthiness of these decisions is based on variance components and error variances derived through generalizability theory.…

Replication is important to viable scientific inquiry; results that will not replicate or generalize are of very limited value. Statistical significance enables the researcher to reject or not reject the null hypothesis according to the sample results obtained, but statistical significance does not indicate the probability that results will be…

A study on sampling errors of variance components was conducted within the framework of generalizability theory by P. L. Smith (1978). The study used an intuitive approach for solving the problem of how to allocate the number of conditions to different facets in order to produce the most stable estimate of the universe score variance. Optimization…

Statistical significance is misused in educational and psychological research when it is applied as a method to establish the reliability of research results. Other techniques have been developed which can be correctly utilized to establish the generalizability of findings. Methods that do provide such estimates are known as invariance or…