POG by chance. The percentage of overlapping genes (POG) increases by chance when the percentage (P) of selected genes (out of candidate genes) increases. For k replicates or platforms compared, the log ratios of the simulated replicates or platforms are assumed to have a normal distribution of N(0,1) and no correlation between each other (LRr2 = 0). The expected POG by chance is 100*(P/2)k-1, where k is the number of replicates or platforms. POG2, POG3, POG4, and POG5 correspond to the comparison of 2, 3, 4, and 5 replicates (or platforms), respectively.