Bayes Rule in an animated gif · Simply Statistics
"Say Pr(A)=5% is the prevalence of a disease (% of red dots on top fig). Each individual is given a test with accuracy Pr(B|A)=Pr(no B| no A) = 90% . The O in the middle turns into an X when the test fails. The rate of Xs is 1-Pr(B|A). We want to know the probability of having the disease if you tested positive: Pr(A|B). Many find it counterintuitive that this probability is much lower than 90%; this animated gif is meant to help."