Patient level (A) vs PCR bacth level (B) resampling strategies. The training dataset includes 5 batches (on the left of the figure). The figure presents an example of patients resampling in a given fold, and a given iteration. In each batch, gene expression of survivor (open circles) and non-survivor (plain circles) patients are measured. In strategy A, samples are randomly drawn within batches to be included in the training fold-data. In strategy B, entire batches are selected and included in the training-fold data. The model building step is performed on the training-fold data and model performance are estimated on the test-fold data.