VisualizationsStatistics and Probability

Bayes' Theorem

Switch a condition between 10% and 1% of people, and a grid of 1,000 squares, one per person, lights up who has it. That share is the base rate.

Bayesian Updating Laboratory

Explore base rates, test accuracy, true vs. false positives, and posterior probability updates.

1. Prior

Prevalence (Base Rate):

Population Grid (N = 1000 | 1 square = 1 person)

Condition Present (100)

Condition Absent (900)

Prior Probability

Condition Present:100

Total Population N:1000

Prior P(Condition):10%

Bayes' Formula Bridge

P(H|E)=

P(E|H) × P(H)P(E)

Prior P(H):0.10

Likelihood P(E|H):0.90

Evidence P(E):0.180

Result:0.5000

Prevalence (Base Rate): Shows how common the condition is in the general population. Note that the Condition Present group is a small minority (10%).

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