Figure 2.

Histogram of Logit-Log slopes. Least-squares linear fits to logit-transformed intensity for each PM probe from the spiked-in probesets in the Affymetrix Latin Square dataset versus log concentration of the spike resulted in slopes constituting the histogram. The major mode of the histogram near -0.15 logit intensity units per log concentration unit represents the majority of probes and is used in the Logit_Exp and Logit_ExpR gene-expression indexes.