hi all, I observed in the Affy latin square experiment more noise between the triplicates of probe sets spiked in at lower concentrations. This is apparent with all summarization techniques used like MAS5 and (GC-)RMA. Did somebody else also detect this tendency? I am looking for an explanation for it. Are these concentrations made in a dilution serie? If so, this increased variation with decreasing concentration might result from the fact that lower concentrations experienced more dilution steps. Or not? Cheers, Willem