Skip to main content Skip to secondary navigation
Page Content

HAI Weekly Seminar with Art Owen

Event Details

Wednesday, September 29, 2021
10:00 a.m. - 11:00 a.m. PDT

Event Type




Kaci Peel

Variable Importance, Cohort Shapley Value, and Redlining

In order to explain what a black box algorithm does, Owen says, we can start by studying which variables are important for its decisions. Variable importance is studied by making hypothetical changes to predictor variables. Changing parameters one at a time can produce input combinations that are outliers or very unlikely.  They can be physically impossible, or even logically impossible. It is problematic to base an explanation on outputs corresponding to impossible inputs. Owen introduces the cohort Shapley (CS) measure to avoid this problem, based on Shapley value from cooperative game theory.

There are many tradeoffs in picking a variable importance measure, so CS is not the unique reasonable choice. One interesting property of CS is that it can detect 'redlining', meaning the impact of a protected variable on an algorithm's output when that algorithm was trained without the protected variable.

Art Owen

Art Owen

Professor of Statistics, Stanford University