Ages 15–18 · Statistics

The Prior Lab

Load a real-shaped rating distribution — or add your own votes — move the dummy-vote block, and watch the shrinkage formula BGG is believed to use pull the rating toward, or away from, the prior at 5.5.

Load a real-shaped game (or build your own below):

Dummy votes in the prior: 100

Advanced: where does the prior sit?

Prior mean (the value each dummy vote holds): 5.5

BGG pins its dummy block at 5.5 (the scale midpoint). Slide it to see how the whole leaderboard shifts — and why a lowering crowd (review-bombing) resists the prior too.

Add your own votes at: 9 stars

Real votes0

Raw average—

Geek Rating (Bayesian)5.50

Prior still weighs100%

Watch the prior wash out — the rating as this crowd grows from 0 votes to its full size: ~ Predicted · worked out by a calculation

0 votes—

How many 9-star votes to reach ?

Add votes to see how many it takes to overcome the prior.

Rank the leaderboard

Here are the same games — you see only the raw average and the number of votes. On a leaderboard with a 4,000-vote prior at 5.5, which one sits highest? Predict first, then reveal.