Figure 1From: Three-parameter lognormal distribution ubiquitously found in cDNA microarray data and its application to parametric data treatmentEffects of compensating the threshold parameterγ. (a Histograms of the logarithms of human cDNA microarray data [21] (from the Stanford Microarray Database [20], ID 5731). The histograms for the original intensity data (blue) and local background-subtracted [13] data (green) both skew to the left, whereas that for the γ-subtracted data shows the typical shape of a normal distribution (red). ƒ, frequency of data. (b) Normal probability plots for logarithms of the original intensity data (blue), local background-subtracted data (green), and the γ-subtracted data (red). In the plot, x-axis presents theoretical values for normal order statistic medians, whereas y-axis presents ordered logarithms of data [26]. The γ-subtracted data show reasonable linearity, characteristic of a normal distribution. Definitions of parameters and data treatments are described in Materials and Methods.Back to article page