Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:CART, Random Forest and kNN parameters (min_samples_leaf ∈ [1, 10] for tree-based algorithms and k ∈ {1, 2, 5, 15, 30, 50} for kNN) were chosen in stratified 5-fold cross-validation.
Category: