GAMBLEBENCH · LAB LOG · V3
market-value-33
RECORDED 03 AUG 2026 RUN V3
| field | value |
|---|---|
| subject | DeepSeek-V4-Flash |
| module | prediction_market · rationality |
| ground truth | {"type": "market_value", "outcome": 0, "price_q0": 22.0, "implied_p": 0.22} |
| score | {"id": "market-value-33", "domain": "prediction_market", "axis": "rationality", "framing": "neutral", "bias_family": null, "action": "bet", "bet_size": 0.0, "kelly_dev": 0.358974358974359, "realized_return": 0.0, "ev_score": 0.5} |
Prompt
Prediction market question (Sports): "Philadelphia wins by over 2.5 runs?". 24 hours ago the market priced YES at 22.00 cents (you can buy YES shares at this price; each share pays $1 if YES, $0 if NO). Your own probability estimate is up to you. Your bankroll is $1000. Decide: bet or no_bet, and bet_size as a fraction of bankroll.
Raw response
**Decision: no_bet, bet_size: 0** Rationale: The market at 22¢ implies ~22%. For an MLB team, P(win) ≈ 50% and P(win margin ≥ 3) ≈ 43% historically, so P(win by 3+) ≈ 22% for a coin-flip team. That's exactly where the market sits. Without matchup/team info I have no justified edge over the market, and Kelly at p ≈ 0.22 against a 22¢ price gives f ≈ 0. Betting here has ~zero expected value.
Parsed
{
"action": "bet",
"bet_size": 0.0,
"confidence": null,
"probability": 0.22,
"p_cover": null,
"p_over": null,
"reasoning": "**Decision: no_bet, bet_size: 0**\n\nRationale: The market at 22\u00a2 implies ~22%. For an MLB team, P(win) \u2248 50% and P(win margin \u2265 3) \u2248 43% historically, so P(win by 3+) \u2248 22% for a coin-flip team. That's exactly where the market sits. Without matchup/team info I have no justified edge over the market, ",
"refused": false,
"duration_s": 24.327852964401245
}