ML 18: A SHAP Value Is an Answer to "Compared With What?"
Disclosure: this post was written with the assistance of an AI system (Claude), which wrote the analysis code, ran the experiments and drafted the text. The topic, the constraints, the data choices and the final review are the author’s. Exact Shapley values, by enumerating all 32 coalitions, for a five-feature gradient-boosted model of the breast-cancer data. Against all training tumours as background, they add up to each prediction minus the mean to within 7e-15....