Source: Downs & Black, 1998 36
NOTE: The Downs and Black checklist is organized into four broad categories: reporting, external validity, internal validity (bias and confounding), and power. Twelve questions not applicable to cross-sectional or cohort studies were removed: questions 4 and 8 (reporting), 12 and 13 (external validity), 14–16, 19, 21, 23 and 24 (internal validity); and 27 (power). The modified scale contained 15-items with a maximum score of 16 possible points: 9 points for reporting (one question had a 2-point option); 1 point for external validity; and 6 points for internal validity.