A probe that is induced or repressed at least twofold in a replicate to was defined as changed. The set of probes that, across replicates marked as Present by MAS5.0, were both (1) changed in at least two replicates and (2) changed on average. The second criterion is redundant when all three replicates are changed, but helps control situations where one replicate is markedly different from the others. These probes have a false discovery rate (FDR) of ~5%.