Pearson correlation of log
ratios for different normalization methods and qRT-PCR. Correlations of log2 ratios were calculated for differently pre-processed gene expression data from BeadChip arrays and qRT-PCR based results. On the x-axis, pre-processing methods are ranked according to their correlation to qRT-PCR. The dashed red lines indicate the cut-offs used for assigning quality score between -2 (< 0.9) and 2 (>0.96).