Global Mean method -cross slide normalization
•A single normalization factor (k) is computed for balancing chips/channels:
•
Xinorm =  k × Xi k = ΣRi/ ΣGi
•
•Multiplying intensities by this factor equalizes the mean (median) intensity among compared chips
–Calculate mean intensity of all spots in channels 1 & 2
e.g. mch1  =  20,000
mch2  =  25,000      
mch2/mch1 = 1.25
–On average, spots in ch2 are 1.25X brighter
than spots in ch1
–To normalize, multiply spots in ch1 by 1.25
Before Normalization
After Scaling