Resolved · 16 May 2026
Where should I host my Eurovision party?
A Denmark-themed party: commit to a premium venue (worth +€500 if Denmark finishes top-5, −€500 if not), or host at home. Before the final — forecast pulled from the production API on 2026-05-12, four days out:
Claude + Internet → book the venue.
Polymarket’s 66.5% is above the 50% breakeven, so expected value looks positive (+€165).
Claude + Credence → host at home.
Credence’s calibrated probability was actually higher — 72.7% — so the point estimate still said book. Its evidence strength was 4.80, fitted from comparable historical forecasts rather than this market. Under an illustrative conservative policy that required stronger group-level evidence before an irreversible commitment, the call was to pass.
Why it mattered: Credence wasn’t “more right” about the odds — in fact it leaned more toward Denmark than the market did. The evidence-strength value described the historical cohort assigned to the forecast, not latent precision for Denmark. Claude used that group-level fact in a conservative commitment rule.
Driving market: Denmark top-5 at Eurovision 2026. Market price 66.5% · calibrated probability 72.7% · group-conditional evidence strength 4.80, pulled from the production API 2026-05-12 — before the 16 May final. Outcome real (Denmark 7th); the venue payoff and decision policy are illustrative. Not advice.
Show Claude’s math
EV (venue − home | p) = 1000 p − 500 ; breakeven p = 50%.
Market mean 0.665 → +€165 (venue). Credence mean 0.727 → +€227 (still venue).
Evidence strength 4.80 describes the assigned historical cohort; it does not create a market-specific precision estimate.
Illustrative policy: do not make the irreversible venue commitment when the assigned cohort’s evidence strength does not clear the decision-maker’s pre-set floor → home.
Assumption: this group-level risk policy. Credence supplies the probability object; it does not prescribe the action or the floor.
Realized 2026-05-16: Denmark 7th, not top-5 → venue −€500, home €0.