MA plots for Classic RMA and refRMA models. Mean probe set intensities as summarized for each of two sets of 15 normal liver samples are shown. The a) Full refRMA model was calculated based on 1,614 biologically diverse samples exclusive of the 30 normal liver test set samples contributing to this plot. The b) Classic RMA model was trained using only the 30 test set samples. Consistency in general data structure is observed regardless of training set. For each probe set, the mean intensity was calculated by averaging individual expression values across the 15 samples in each set.