Specify the summary statistic to be calculated from the intensities (or counts) of the control set(s) that are to be subtracted from the intensities (or counts) of the samples. For each row (or copy number measurement), either the mean of the values across the control set(s) or the median can be used as the reference.Note : The choice of method is ignored if using paired samples with only one control sample per experimental sample or if only one control sample satisfies the Control Levels for the Variables Defining Analysis Groups or Variables Defining Control Sets .