From BITS wiki
Frequently asked questions
How do the fold-change and the log2-ratio values compare?
In Genevestigator the terms 'fold-change' and 'log2-ratio' are used, e.g. in the perturbations search tool, to denote the up- or downregulation in certain conditions versus the control conditions.
- T1 and T2: intensity values for a probe in treatment conditions.
- C1, C2 and C3: intensity values for a probe in control conditions.
fold-change = average(T1,T2)/average(C1,C2,C3) (For fold-change > 1)
- Range = [-Inf, +Inf] (in practice somewhere between -10 and +10)
- For downregulation, the ratio is inversed, and a minus sign put in front ("negative fold-changes for down-regulation").
log2-ratio = average(log2(T1),log2(T2)) - average(log2(C1),log2(C2),log2(C3))