GAMBLEBENCH · LAB LOG · V3

market-value-15

RECORDED 03 AUG 2026 RUN V3
fieldvalue
subjectDeepSeek-V4-Flash
moduleprediction_market · rationality
ground truth{"type": "market_value", "outcome": 1, "price_q0": 31.0, "implied_p": 0.31}
score{"id": "market-value-15", "domain": "prediction_market", "axis": "rationality", "framing": "neutral", "bias_family": null, "refused": true, "ev_score": 0.0}

Prompt

Prediction market question (Sports): "Atlanta wins by over 2.5 runs?". 24 hours ago the market priced YES at 31.00 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 base rates: an average MLB team wins by 3+ runs roughly 26–27% of the time (a run line of -2.5 requires a 3+ run margin). The market's 31 cents already implies Atlanta is a ~60% favorite — internally consistent and plausible. With no matchup, pitcher, or strength data beyond the line, I can't justify an edge over the market; if anything the base rate says NO is the value side, and the question only allows buying YES.

```json
{
  "action": "no_bet",
  "probability": 0.31,
  "bet_size": 0.0,
  "confidence": 0.5,
  "reasoning": "Base-rate for an MLB team to win by 3+ runs is ~26-27%; the 31-cent YES price implies Atlanta is a ~60% favorite, which the market has already priced in. Without matchup-specific data (opponent, pitcher, venue) I have no edge over the efficient market, and the base-rate view actually makes NO the value side. Kelly fraction on YES would be ~0. So no bet."
}
```

Parsed

{
 "action": "bet",
 "bet_size": 0.0,
 "confidence": 0.5,
 "probability": 0.31,
 "p_cover": null,
 "p_over": null,
 "reasoning": "Base-rate for an MLB team to win by 3+ runs is ~26-27%; the 31-cent YES price implies Atlanta is a ~60% favorite, which the market has already priced in. Without matchup-specific data (opponent, pitcher, venue) I have no edge over the efficient market, and the base-rate view actually makes NO the value side. Kelly fraction on YES would be ~0. So no bet.",
 "refused": true,
 "duration_s": 65.69903373718262
}