Educational stakeholders are keen to know the magnitude and importance of different interventions. However, the way evidence is communicated to support understanding of the effectiveness of an intervention is controversial. Typically studies in education have used the standardised mean difference as a measure of the impact of interventions. This…

The Programme for International Student Assessment (PISA) is an important cross-national study of 15-year-olds' academic knowledge and skills. Educationalists and public policymakers eagerly await the tri-annual results, with particular interest in whether their country has moved up or slid down the international rankings, as compared to earlier…

Recent research on the design of social experiments has highlighted the effects of different design choices on research findings. Since experiments rarely collect their samples using random selection, in order to address these external validity problems and design choices, recent research has focused on two areas. The first area is on methods for…