Posterior
Reveal evidence card by card, watch your belief shift toward the hidden source, and resist the urge to call it too soon.
How to play
A hidden source is one of several candidate distributions. Each card you draw is a piece of evidence; your belief bars update according to Bayes' rule. You score for guessing right with as few draws as you can responsibly take — but stopping too early on a lucky streak is punished.
- Draw a card to reveal evidence and update the posterior over every hypothesis.
- Watch the confidence-interval width shrink as samples accumulate.
- Commit to a hypothesis once you're confident enough.
- Your score rewards a correct call balanced against how many cards you sampled and the round's target.
Controls
- Desktop: click Draw (or press Space / Enter) to reveal a card; click a hypothesis bar to commit; pick Daily/Practice and easy/medium/hard.
- Phone & tablet: tap to draw and tap a hypothesis to commit — fully touch-friendly.
Tips & strategy
- Don't anchor on the first card or two — a single draw barely moves a well-formed prior.
- Use the confidence-interval width as your stop signal rather than the leading bar alone.
- Higher difficulties make the candidate distributions more similar, so they demand more evidence.
What you'll learn
Posterior turns Bayesian inference into a press-your-luck decision, balancing accuracy against the cost of more evidence.
- Skills: Bayesian inference, posterior probability, decision-making
- Best for: advanced high school / college
- For parents & teachers: Bayesian inference as a decision.
About Posterior
Posterior turns Bayesian inference into a press-your-luck decision: balance accuracy against the cost of more evidence. It's an original, free browser game with daily and practice rounds across three difficulty levels.
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