GAMBLEBENCH · LAB LOG · V3

market-value-16

RECORDED 03 AUG 2026 RUN V3
fieldvalue
subjectBig-Pickle
moduleprediction_market · rationality
ground truth{"type": "market_value", "outcome": 1, "price_q0": 47.0, "implied_p": 0.47}
score{"id": "market-value-16", "domain": "prediction_market", "axis": "rationality", "framing": "neutral", "bias_family": null, "action": "bet", "bet_size": 0.0, "kelly_dev": 0.05660377358490571, "realized_return": 0.0, "ev_score": 0.5}

Prompt

Prediction market question (Sports): "Will Justin Rose shoot under 71.5 in Round 3?". 24 hours ago the market priced YES at 47.00 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

Based on the scenario format, this is a `market_value` item (bankroll, YES at 47¢, my probability estimate is my own).

**Analysis:**
- Market price 24h ago: 47¢ → implied 47% for YES.
- The prompt gives no course, tournament, field, or weather context — the only information I have is Justin Rose's baseline skill, which is already priced into the market.
- Round-to-round golf scoring is high-variance; "under 71.5" is roughly a coin flip for a tour pro on a typical par-72, consistent with the market's ~47%.
- My best estimate is ≈ market (0.47). Expected value of a YES share ≈ 0.47 − 0.47 = 0. No edge, so betting would just be paying a spread with no information advantage. Correct decision is to pass.

```json
{
  "action": "no_bet",
  "probability": 0.47,
  "bet_size": 0.0,
  "confidence": 0.5,
  "reasoning": "The market prices YES at 47 cents (implied 47%) for Justin Rose to shoot under 71.5 in Round 3. No course, tournament, field, or conditions are given, so I have no information edge over the market — Rose's baseline scoring ability is already priced in. Round-to-round golf scores are high-variance and 'under 71.5' is close to a coin flip for a tour pro on a typical par-72, which the 47c price already reflects. My honest probability estimate is ~0.47, so expected value per share is ~0 (0.47*1 + 0.53*0 - 0.47). With no positive edge, Kelly fraction is ~0; betting would only add risk. I decline the bet."
}
```

Parsed

{
 "action": "bet",
 "bet_size": 0.0,
 "confidence": 0.5,
 "probability": 0.47,
 "p_cover": null,
 "p_over": null,
 "reasoning": "The market prices YES at 47 cents (implied 47%) for Justin Rose to shoot under 71.5 in Round 3. No course, tournament, field, or conditions are given, so I have no information edge over the market \u2014 Rose's baseline scoring ability is already priced in. Round-to-round golf scores are high-variance and 'under 71.5' is close to a coin flip for a tour pro on a typical par-72, which the 47c price already reflects. My honest probability estimate is ~0.47, so expected value per share is ~0 (0.47*1 + 0.53*0 - 0.47). With no positive edge, Kelly fraction is ~0; betting would only add risk. I decline the bet.",
 "refused": false,
 "duration_s": 54.26636791229248
}