Table A.2.

Strength-of-Evidence (Level-of-Certainty) Designations

Level	Description
Strong	Two or more Level 1a studies The available evidence usually includes consistent results from well-designed, well-conducted studies. The findings are strong, and they are unlikely to be strongly called into question by the results of future studies.
Moderate	At least 1 Level 1a or multiple moderate-quality studies (e.g., Level 2a) The available evidence is sufficient to determine the effects on health outcomes, but confidence in the estimate is constrained by such factors as ∘ number, size, or quality of individual studies and ∘ inconsistency of findings across individual studies. As more information (other research findings) becomes available, the magnitude or direction of the observed effect could change, and this change may be large enough to alter the conclusion related to the usefulness of the intervention.
Low	Small number of low-level studies, flaws in the studies, and so on The available evidence is insufficient to assess effects on health and other outcomes of relevance to occupational therapy. Evidence is insufficient because of ∘ limited number or size of studies, ∘ important flaws in study design or methods, ∘ inconsistency of findings across individual studies, and ∘ lack of information on important health outcomes. More information may allow estimation of effects on health and other outcomes of relevance to occupational therapy.