HighWe are very confident that the true effect lies close to that of the estimate of the effect.
ModerateWe are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect but there is a possibility that it is substantially different.
LowOur confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect.
Very lowWe have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

From: ANNEX 2, Systematic Review and Guideline Methods

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WHO Guidelines for the Pharmacological and Radiotherapeutic Management of Cancer Pain in Adults and Adolescents.
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