Table 2 Study validity categories.
Quality | Replication | Sample selection | Other sources of bias |
|---|---|---|---|
High | Well-replicated (> 10 individuals per group) | Random | None |
Medium | Moderate level of replication (5–10 individuals per group) | Not stated but clearly random | Potential confounder |
Low-Poor | Poorly replicated or not stated (1–4 individuals per group) | Purposive or not stated | Clear confounder e.g., repeated measures on same individuals |