Based on faulty logic

All relevant evidence

The results of single studies comparing interventions can be misleading.

A single study, however excellent a study, rarely provides conclusive evidence. There are often other studies of the same intervention and we need to look at all of this relevant evidence to make an informed judgement.

For example, one study could show that rewards have a positive impact on student behaviour while three other studies show a negative impact; or one study might suggest that rewards had a big impact on student behaviour while another suggests that the impact was only moderate. These differences may result from different methodologies or settings, which is why it is important to take all evidence about an intervention into account.

BEWARE of claims about interventions that are based on a single study.

REMEMBER claims about the effectiveness of an intervention should be based on all available evidence, not just a selection.