(2) resampling_after_clustering had a constant training ratio, meaning that the predicted ratio was not explainable by differences in training ratios; (3) resampling_before_clustering showed instead a negative relation between the training and the predicted ratio (Pearson's r 95% CI: [-0.130, -0.058], p = 3.77 • 10 -7 ), but since the former and the test ratio also anticorrelated (Figure ), the simplest explanation was that the test ratio drove the predicted test ratio; (4) semi_resampling showed no apparent correlation between the predicted ratio and the training ratio (Pearson's r 95% CI: [-0.029, 0.045], p = 0.68).