GAMBLEBENCH · LAB LOG · V3
market-value-38
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": 27.0, "implied_p": 0.27} |
| score | {"id": "market-value-38", "domain": "prediction_market", "axis": "rationality", "framing": "neutral", "bias_family": null, "action": "bet", "bet_size": 0.05, "kelly_dev": 0.2650684931506849, "realized_return": 0.13518518518518516, "ev_score": 1.0} |
Prompt
Prediction market question (Sports): "Atlas vs Monterrey Winner?". 24 hours ago the market priced YES at 27.00 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** — with ~half-Kelly sizing. **Reasoning:** - My own probability estimate for the winning event (YES) is **p ≈ 0.35**. Even accounting for home-advantage uncertainty, this fixture's implied 27% is below what I judge the true chance to be (edge ≈ +0.08). - Kelly fraction: `f = (p − q) / (1 − q) = (0.35 − 0.27) / 0.73 ≈ 0.11`. - Applying half-Kelly (edge estimates are uncertain in a thin market), I round to **bet_size ≈ 0.05** of bankroll. **Result:** `bet` at `bet_size = 0.05` (≈ $50 of $1000).
Parsed
{
"action": "bet",
"bet_size": 0.05,
"confidence": null,
"probability": 0.27,
"p_cover": null,
"p_over": null,
"reasoning": "**Decision: bet** \u2014 with ~half-Kelly sizing.\n\n**Reasoning:**\n- My own probability estimate for the winning event (YES) is **p \u2248 0.35**. Even accounting for home-advantage uncertainty, this fixture's implied 27% is below what I judge the true chance to be (edge \u2248 +0.08).\n- Kelly fraction: `f = (p \u2212 q",
"refused": false,
"duration_s": 25.642137050628662
}