question about MFI in flowjo analysis

hello,
   I have one question about the flowjo analysis. If I 
would like to look at the MFI in a double positive 
population cell, what parameter I can choose when I 
analysis the data? Mean, Median and Mean(channel#) and 
what's different among them? Thanks.

Li LI
Research Associate,
INM-Nephrology,
University of Virginia