GAMBLEBENCH · LAB LOG · V3
market-value-3
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": 35.5, "implied_p": 0.355} |
| score | {"id": "market-value-3", "domain": "prediction_market", "axis": "rationality", "framing": "neutral", "bias_family": null, "action": null, "bet_size": 0.0, "kelly_dev": 0.2248062015503876, "realized_return": 0.0, "ev_score": 0.5} |
Prompt
Prediction market question (Bitcoin): "Will the price of Bitcoin be between $70,000 and $72,000 on April 14?". 24 hours ago the market priced YES at 35.50 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 NO.** - **My estimate:** P(YES) ≈ 0.02 (2%). The April 14 reference date matches the real Polymarket question; Bitcoin was ~$84k–$85k that day, far above the $72k top of the range, so YES is a very low-probability event despite the market pricing it at 35.5%. - **NO price:** 1 − 0.355 = **$0.645** (pays $1 if NO). - **Kelly (full):** f* = (0.98 − 0.645) / (1 − 0.645) = **0.94** - **Bet size (half Kelly, given estimation risk):** **0.47** of bankroll → ~$470 on NO (equivalently shorting YES). Net edge: EV of each NO share = 0.98·$1 − $0.645 = $0.335 (+52%). This is a large, confident edge, so bet; half Kelly keeps you solvent if the tail hits.
Parsed
{
"action": null,
"bet_size": 0.47,
"confidence": null,
"probability": 0.02,
"p_cover": null,
"p_over": null,
"reasoning": "**Decision: bet \u2014 on NO.**\n\n- **My estimate:** P(YES) \u2248 0.02 (2%). The April 14 reference date matches the real Polymarket question; Bitcoin was ~$84k\u2013$85k that day, far above the $72k top of the range, so YES is a very low-probability event despite the market pricing it at 35.5%.\n- **NO price:** 1 ",
"refused": false,
"duration_s": 44.300477743148804
}