Table 1. National Health and Medical Research Council hierarchy of evidence-based scientific studies.

Level	Intervention
I	A systematic review of level II studies
II	A randomized controlled trial
III-1	A pseudorandomized controlled trial (ie, alternate allocation or some other method)
III-2	A comparative study with concurrent controls:  Non-randomized experimental trial  Cohort study  Case–control study  Interrupted time series with a control group
III-3	A comparative study without concurrent controls  Historical control study  Two or more single-arm study  Interrupted time series without a parallel control group
IV	Case series with either post-test or pretest/post-test outcomes