[BioC] M Value

Eric Frapy eric.frapy at inserm.fr
Mon Oct 6 17:29:16 CEST 2008

I used Limma to analyze microarray data.
I have a question with M value.
Is it correct that M value correspond to Log2(Signal in Cy5) - 
Log2(Signal in Cy3)?
So if the difference equal to zero, it means that there is no difference 
beetween two sample.
I want to know how to have a "true" fold value with the M value ?
I mean if I have M Value = -4.685278 it mean that we have a difference 
beetween Cy5 and Cy3 intensity log2 value, so that "gene" is over 
expressed in Cy3 but with which value, 2 times, 3 times, 6 times.....?
So in fact my question is how to transform the M value, in over 
expressed value ?
Then i can compare this over expressed value with the value obtain in RT 
PCR Real Time.



More information about the Bioconductor mailing list