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Table 3 Designations of levels of evidence as proposed by NHMRC.

From: Idiopathic toe walking and sensory processing dysfunction

Level Aetiology
I A systematic review of level II studies
II A prospective cohort study
III-1 All or none§§§
III-2 A retrospective cohort study
III-3 A case-control study
IV A cross-sectional study/case series
  1. §§§ All or none of the people with the risk factor(s) experience the outcome. For example, no smallpox develops in the absence of the specific virus; and clear proof of the causal link has come from the disappearance of small pox after large-scale vaccination.
  2. Modified from "Designations of levels of evidence* according to type of research question (including tablenotes)" [72, 73]