Population stability index

A number that measures how much the population a model sees has shifted away from the population it was built on. A higher value means more drift. It is one of the concrete triggers proposed for when a deployed AI tool needs re-checking: a population stability index above 0.2 is a common threshold for "investigate this". A practical early-warning signal that the data environment around a model has changed.

Terms like this come up in real clinical scenarios across the HelloAI courses: bite-sized modules with verifiable certificates. An account takes one minute, no password needed.