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. 2017 Sep 8;6:337. doi: 10.4102/ajod.v6i0.337

TABLE 1.

Hierarchy of evidence.

Levels Types of literature
Level 1 Systematic review
Level II-1 Randomised control trials
Level III-1 Pseudo-randomised controlled trial
Level III-2 Comparative study with concurrent controls
Level III-3 Comparative study without concurrent controls
Level IV Case series/studies with either post-test or pre-test/post-test outcomes

Source: Abdullah et al. 2012