AI engineering glossary · Probability
What is base rate?
Base rate (also called Prevalence): The overall proportion of a population that has some characteristic, before considering any specific evidence. Ignoring it leads to badly wrong conclusions, especially when the characteristic is rare. It is the baseline against which any test result should be judged.
Base rate: an example
If only 1 in 1,000 transactions is fraud, the base rate is 0.1%, so even a good detector produces mostly false alarms.
Related terms
More Probability terms
- Base rate fallacy
- Bayes' theorem
- Bayesian probability
- Bernoulli distribution
- Binomial distribution
- Birthday problem
- Categorical distribution
- Central limit theorem
Where you learn it
Base rate is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.