Density plot of a single EBV-transformed cell. (a,b) Density plot for EBV-transformed single lymphoblastoid cell 1162 before normalization (a), and after channel standardization (b). The solid line represents the reference sample and the dashed line represents the test sample. Note that the SD of the intensities of the test sample (SD = 1.02) is larger than that of the reference sample (SD = 0.61). (c,d) QQ plot of the intensities between the test and the reference samples before normalization (c), and after channel standardization (d).