Discussion chapter

The use of effect sizes in a keenly debated topic and one that it is seen as an important issue in educational research and evaluation for policy making. This chapter discusses the comments made at the invitational seminar, jointly organised by the Institute of Education, University of London and the National Foundation for Educational Research (NFER) on 14 November 2003 and the contributions received from the discussion forum that was available for a month after the event. It emerged from the discussion that there is no best effect size measure. Different measures of effect size are required for different questions. However, it was also highlighted that more agreement on the best approaches to calculate effect sizes under different circumstances is needed. Earlier on this chapter it was also indicated that relying on the p-value alone when presenting results may be inappropriate and could lead to misreporting. There was a core agreement regarding the need for practitioners and policy makers to combine value/weight/significance measures to research findings. It was also noted that policy makers and practitioners require the output from the educational research establishment to be both clear and persuasive. Besides, caution is required against over complicated analyses without justification. However, it was also noted that simple models may need to be confirmed by more complex models which take into consideration more background factors and relationships.