FA-84783 / Betting odds conversion / Member archive

Double-chance price averaged instead of combined · case 03

Double-chance prices sit between the two single prices.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Derive secondary markets from 1X2 decimal prices [home, draw, away], keeping the original margin. Draw no bet side price = side * (1 - 1/draw). Double chance for two outcomes p, q = p * q / (p + q): 1X from home and draw, 12 from home and away, X2 from draw and away. Return a dict with keys dnb_home, dnb_away, 1X, 12, X2, values rounded half up to two decimals.

Why this case matters

Sportsbooks price derived markets from the main 1X2 line.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
control balanced match	`{"12": "2.75", "1X": "2.85", "X2": "3.10", "dnb_away": "2.06", "dnb_home": "1.72"}`	`{"12": "1.36", "1X": "1.40", "X2": "1.55", "dnb_away": "2.06", "dnb_home": "1.72"}`	Failed

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