GAMBLEBENCH · LAB LOG · V3
market-value-9
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": 41.0, "implied_p": 0.41} |
| score | {"id": "market-value-9", "domain": "prediction_market", "axis": "rationality", "framing": "neutral", "bias_family": null, "action": "bet", "bet_size": 0.0, "kelly_dev": 0.15254237288135594, "realized_return": 0.0, "ev_score": 0.5} |
Prompt
Prediction market question (Sports): "Seattle vs San Diego First Inning Run?". 24 hours ago the market priced YES at 41.00 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
My fair estimate: a first-inning run in an MLB game happens ~28–31% of the time (base rate). The market is pricing YES at 41%, which is well above that — so there's edge on **NO** (buyable at 59¢). Kelly for buying NO at price P with true prob q: `(q − P)/(1 − P) = (0.70 − 0.59)/(1 − 0.59) ≈ 27%`. **Decision: bet** on NO, size **~0.14 of bankroll** (half-Kelly, given estimate uncertainty) ≈ **$140**.
Parsed
{
"action": "bet",
"bet_size": null,
"confidence": null,
"probability": 0.31,
"p_cover": null,
"p_over": null,
"reasoning": "My fair estimate: a first-inning run in an MLB game happens ~28\u201331% of the time (base rate). The market is pricing YES at 41%, which is well above that \u2014 so there's edge on **NO** (buyable at 59\u00a2).\n\nKelly for buying NO at price P with true prob q: `(q \u2212 P)/(1 \u2212 P) = (0.70 \u2212 0.59)/(1 \u2212 0.59) \u2248 27%`.\n",
"refused": false,
"duration_s": 29.174108028411865
}