Hi, I need to calculate some data regarding the variance of probes across samples. Typically we have expressed this as the relative standard deviation before. However, I have only done this for 1 colour data previously and the dataset I am working with is 2 colour common reference data. When I repeat what I did previously using the Ratio I see very strange (High) percentages. When I use only target channel I see percentages like before. What am I not understanding about the ratio that is preventing me from calculating this? Any and all help gratefully received. Thanks Elliott [[alternative HTML version deleted]]