PBM data quality for TF_7 (Mix) and TF_63 (Zkscan5). A and B are MA scatter plots of TF_7 and TF_63, respectively. C and D are scatter plots of Z-score transformed 8-mer median intensities between a pair of training and testing PBM experiments for TF_7 and TF_63, respectively. In the figure, the red ellipses are 99.73% limit of PCA quality-control ellipses, the two red smooth lines are the length of the major and minor axes of the PCA ellipses, the black smooth lines are fitted linear regression lines, and the green data points are observations that may be out of the quality control (i.e. data point outside of the PCA ellipse and one of the observations is below sample mean).