The second method used the average expression level for each treatment group for filtering and was applied to both the MAS5 and RMA datasets For each probe set, MAS5 signals and RMA values were averaged for each treatment group separately. A probe set was retained if the average expression level (MAS5 signal or RMA value) met or exceeded the selected threshold value in at least one treatment group. For example, using a filter of 100 for the MAS5 signal, probe sets are retained if the average signal for either treatment group met or exceeded 100.
