What's the difference between Reference target stability and geNorm?
geNorm was developed to support selection of the best set of reference genes from a list of measured candidate reference genes. It's typically applied to pilot studies that are only meant to select reference genes.
The reference target stability quality control can be applied to verify whether the selected reference genes allow for reliable normalization. This quality control can be applied to all experiments in which at least two reference genes are included.
In both cases, the calculation of the M-value is based on the same principle, described in (Vandesompele et al., Genome Biology, 2002). The geNorm algorithm uses the M-value calculation in an iterative process to zoom in onto the most stably expressed candidate reference genes.