Evidence Engine
Method & weights
Nothing here is a black box. Every weight that goes into a grade is published below. Back to the engine.
1 · Design weight
Study designs differ in how much they can tell us. Each design has a base weight:
| Randomized controlled trial | 1.00 |
| Cohort study | 0.60 |
| Observational study | 0.35 |
| In-vitro / lab study | 0.15 |
2 · Sample-size factor
Bigger studies count for more, with diminishing returns (log scale). Final study weight = design weight × size factor.
| n = 1 | ×0.40 |
| n = 10 | ×0.60 |
| n = 100 | ×0.80 |
| n = 1,000 | ×1.00 |
| n = 10,000 | ×1.20 |
3 · Result direction
A study's result signs its weight — supporting evidence pushes the grade up, null results push it down, mixed results add weight but no direction (which dilutes support).
| Supports the claim | +1 |
| Mixed / partial | 0 |
| Null result (no effect) | -1 |
4 · How the score is built
score.formula
score = 100 × support × strength × consistencysupport = (signedWeight / totalWeight + 1) / 2strength = 1 − e^(−totalWeight / 1.0)consistency = 0.55 + 0.45 × agreementsingle-study cap = 84 (one study can never reach A)
5 · Grade bands
A90 – 100
A-85 – 89
B+80 – 84
B75 – 79
B-70 – 74
C+65 – 69
C60 – 64
C-55 – 59
D+50 – 54
D40 – 49
D-0 – 39