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Table 2 Grades of recommendation (reproduced with the permission of the SIGN group)

From: Effects of Tai Chi exercises on self-efficacy and psychological health

Grades of recommendation

1++

High quality meta-analyses, systematic reviews of RCTs, or RCTs with a very low risk of bias

1+

Well conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias

1

Meta-analyses, systematic reviews of RCTs, or RCTs with a high risk of bias

2++

High quality systematic reviews of case control or cohort or studies

High quality case-control or cohort studies with a very low risk of confounding, bias, or chance and a high probability that the relationship is causal

2+

Well conducted case-control or cohort studies with a low risk of confounding, bias, or chance and a moderate probability that the relationship is causal

2

Case control or cohort studies with a high risk of confounding , bias, or chance and a significant risk that the relationship is not causal

3

Nonanalytic studies, e.g., case reports, case series

  1. RCT Randomized controlled trial