Why we need an evidence hierarchy
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Evidence hierarchy: Why we need it

Hierarchies of evidence save time.

Nobody has time to read every piece of information available about teacher professional development. For example, searching for the phrases 'professional development' and 'teacher' in just one research database returns over 19,000 records, and not all of them would be of equal relevance.

A researcher, working full time, would need:

5 years to read all relevant articles

Therefore, it is important to distinguish research that provides a strong indication of the direct impact of a program from research that is less able to do this. When the evidence provides stronger indications of outcomes, there can be greater confidence that replicating the program will lead to similar outcomes.