When performing a meta-analysis unexplained variation above that predicted by within study variation is usually modeled by a random effect. However, in some cases, this is not sufficient to explain all the variation because of outlier or unusual studies. A previously described method is to define an outlier as a study requiring a higher random…

Within the emerging field of research on education for sustainability (EfS), case studies are an important if not the predominant research approach, although often criticised for its lack of internal and external validity and a tendency to draw conclusions with insufficient rigour. While, basic concerns have been expressed and discussed in an…

In several subdomains of the social, behavioral, health, and human sciences, research questions are increasingly answered through mixed methods studies, combining qualitative and quantitative evidence and research elements. Accordingly, the importance of including those primary mixed methods research articles in systematic reviews grows. It is…

Problem-based learning (PBL) is an instructional strategy that is poised for widespread application in the current, growing, on-line digital learning environment. While enjoying a track record as a defensible strategy in face-to-face learning settings, the research evidence is not clear regarding PBL in on-line environments. A review of the…