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Table 1 Systematic review case example: helmets for preventing head, brain, and facial injuries in bicyclists

From: Observational evidence and strength of evidence domains: case examples

Strength of evidence factors Strength of evidence domains
Required domains Study limitations:
 • Reduced risk of selection bias: controls from the same population as cases
 • Reduced risk of detection bias: independent outcome assessors
Consistency: consistent direction of effect for the primary outcome observed across multiple studies
Precision: precise effect estimate across included studies
Additional domains Strength of association: large magnitude of effect