GAMBLEBENCH · LAB LOG · V3
market-value-39
RECORDED 03 AUG 2026 RUN V3
| field | value |
|---|---|
| subject | DeepSeek-V4-Flash |
| module | prediction_market · rationality |
| ground truth | {"type": "market_value", "outcome": 1, "price_q0": 11.0, "implied_p": 0.11} |
| score | {"id": "market-value-39", "domain": "prediction_market", "axis": "rationality", "framing": "neutral", "bias_family": null, "action": null, "bet_size": 0.0, "kelly_dev": 0.43820224719101125, "realized_return": 0.0, "ev_score": 0.5} |
Prompt
Prediction market question (Sports): "Houston wins by over 26.5 points?". 24 hours ago the market priced YES at 11.00 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: bet** on YES (Houston covers 26.5+). My probability estimate: **~14%** (slightly above the market's 11% — blowout margins of 27+ pts are rare but not 1-in-9). Expected value check (buy at $0.11/share, $1 payoff): - If YES: profit $0.89/share → net odds b ≈ 8.1:1 - EV = 0.14·0.89 − 0.86·0.11 ≈ **+0.03 per share** (positive, but thin) Kelly fraction: f = p − (1−p)/b ≈ 0.14 − 0.106 ≈ **3.4%** of bankroll. **bet_size: 0.04** (≈ $40 on YES; rounded up slightly from Kelly since the estimate has real uncertainty). I'd cap it there — a small, positive-EV position, not a swing. Caveat: without knowing the teams/line I'm leaning only mildly above the market; if your own estimate is ≤11%, the correct call is no_bet.
Parsed
{
"action": null,
"bet_size": 0.04,
"confidence": null,
"probability": 0.14,
"p_cover": null,
"p_over": null,
"reasoning": "**Decision: bet** on YES (Houston covers 26.5+).\n\nMy probability estimate: **~14%** (slightly above the market's 11% \u2014 blowout margins of 27+ pts are rare but not 1-in-9).\n\nExpected value check (buy at $0.11/share, $1 payoff):\n- If YES: profit $0.89/share \u2192 net odds b \u2248 8.1:1\n- EV = 0.14\u00b70.89 \u2212 0.86",
"refused": false,
"duration_s": 30.677690029144287
}