Population Stability Index (PSI)
A statistical measure of how much a variable's distribution has shifted between two samples, widely used for input-drift detection. A common rule of thumb from credit scoring: below 0.1 is little change, 0.1 to 0.2 is moderate, and above roughly 0.2 to 0.25 is significant. A convention to adjust by consequence, not a law. Its value depends on how the variable is bucketed, so compute it with the same bucket boundaries on the live sample and the baseline every time, or the number is not comparable across checks.
Defined in 2 GAGE programs, which carry 2 distinct definitions of it. The wording above is taught in AI Governance: Applied Mastery.
How each discipline defines it
The same term does different work depending on who is using it. These are the definitions as each program teaches them, unedited.
A statistical measure of how much a variable's distribution has shifted between two samples, widely used for input-drift detection. A common rule of thumb from credit scoring: below 0.1 is little change, 0.1 to 0.2 is moderate, and above roughly 0.2 to 0.25 is significant. A convention to adjust by consequence, not a law. Its value depends on how the variable is bucketed, so compute it with the same bucket boundaries on the live sample and the baseline every time, or the number is not comparable across checks.
A common measure of how much a data distribution has shifted from a baseline. Rule of thumb: under 0.1 is no meaningful drift, 0.1 to 0.2 is moderate (investigate), above 0.2 is significant (act).
Where it is taught
The exact lessons this term appears in. The first 7 topics of every program are free with a free account.
- Model drift: detecting the quiet degradation nobody reports · Evaluation and Trust, AI Governance: Applied Mastery
- Analytics, Telemetry and Observability · Technology, Platforms and Vendors, Business AI Transformation
Terms it appears with
Not an alphabetical neighbourhood: these are the terms taught in the same lessons, ranked by how often they appear together.