{
  "slug": "grouped-cross-validation",
  "term": "Grouped cross-validation",
  "aliases": [
    "group-wise cross-validation",
    "group-aware cross-validation"
  ],
  "definition": "Grouped cross-validation evaluates a predictor using splits that keep all observations from each specified group together in either training or testing within a split.",
  "note": "GroupKFold holds each group out once across its test folds. [sklearn-groupkfold] In storage evaluation, group by physical drive to test unseen drives or by site to test unseen sites; these are different generalization questions. Group separation alone does not impose chronological order. [sklearn-validation]",
  "limitations": [
    {
      "text": "Choose groups for the deployment question; grouping does not prevent future information or globally fitted preprocessing from entering training.",
      "citationIds": [
        "sklearn-validation"
      ]
    }
  ],
  "related": [
    "temporal-validation",
    "prediction-horizon",
    "class-prevalence",
    "smart"
  ],
  "citations": [
    {
      "id": "sklearn-groupkfold",
      "title": "scikit-learn: GroupKFold, non-overlapping groups and per-fold behavior.",
      "url": "https://scikit-learn.org/stable/modules/generated/sklearn.model_selection.GroupKFold.html",
      "accessed": "2026-10-14"
    },
    {
      "id": "sklearn-validation",
      "title": "scikit-learn: cross-validation for grouped data, time series and training-only transformations.",
      "url": "https://scikit-learn.org/stable/modules/cross_validation.html",
      "accessed": "2026-10-14"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-14"
}