Conjugate prior. Beta is conjugate to Binomial: the posterior is another Beta. More data = narrower distribution = more certainty about θ.
Prior to Posterior - Interactive Visualization
Bayesian inference updates beliefs as data arrives: posterior ∝ likelihood × prior. The Beta-Binomial model is the canonical example: Beta prior + Binomial likelihood = Beta posterior. Start with a prior belief about coin fairness (α, β), then observe coin flips. Each flip updates the posterior - more data swamps the prior. This is the essence of Bayesian learning.
Set prior beliefs with α and β sliders for the Beta distribution
Click Flip Coin to observe one flip and update posterior live
Watch posterior narrow as more flips are observed (uncertainty reduces)
See that strong priors (large α, β) require more data to be overcome
Foundation for Bayesian neural networks, Thompson sampling, and A/B testing
Part of the EngineersOfAI Interactive 3D - free interactive visualizations covering every major concept in machine learning and AI engineering. Hover any element for a plain-English explanation. No code required.