Probe intensities as a function of the number of washing cycles: Part a: The probes of three probe sets were selected for large (top row), intermediate (middle row) and low (bottom row) intensity levels (array A; see also Figure 1). The thick lines are the log-mean values averaged over the eleven probes of each probe set. The intensities of PM- and MM-probes and of their log-difference are shown from left to the right as indicated in the figure. Part b re-plots the averaged intensity data of the PM and MM shown in part a after normalization assuming a common start value of w(0) = 1 (symbols). The curves are calculated using Eq. (8).