Error bars for qPCR; technical vs. biological replicate - (Dec/20/2011 )
ABI has a step by step guide for qPCR statistics that ultimately gives you the fold change and the standard deviation (can be found here). My assumption is that the calculated SD only represents the variation in technical replicates and not the biological replicates.
How would you incorporate the variations in both technical and biological replicates into the final error bars (say SD)? Is the technical replicate SD is reflected in the final result at all?
any input is highly appreciated.
From what I have seen, most people just plot technical replicates +/- error bars (95% CIs) and then they indicate that they repeated the experiment 2 or 3 times and had similar results. I think for biological replicates you are correct in assuming that you just ignore the SD for the technical replicates and just calculate the mean and SD for the biological replicates.
Yes, we take SD of technical replicates as a indication how precise was the experiment, but if we plott biological replicates, we only calculate SD for the biological ones and ignore the technical.