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Table 3 Criteria for assessing the overall quality of an environmental study, using the Environmental-GRADE Tool, adapted from the GRADE approach used by the Cochrane Collaboration (Balshem et al. [69]; Schünemann et al. [45]; Guyatt et al. [70])

From: Quality assessment tools for evidence from environmental science

Underlying methodology Quality rating Interpretation
RCT; or double-upgraded observational study. High We are very confident that the true effect estimate lies close to that of the estimate of the effect.
Downgraded RCT; or upgraded observational study. Moderate We 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.
Double-downgraded RCT; or observational study. Low Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect.
Triple-downgraded RCT; or downgraded observational study; or case study. Very low We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect.