How to do graphs with mean value plus error bars for replicates? St deviation or - (Apr/07/2008 )

Dear All,

I have been doing a time course experiment (analysed by Real Time PCR) and I have repeated it 3 times (independently), obtaining 3 different and independent sets of results for the same time course.

I want to represent it in a graph with columns and error bars, but I am not too sure of how to do it and what statistical commands to use in Excel.

As far as I know, the average between the 3 values for a certain time point would be used for the column, right? But how about the error bars? Do we use standard deviation for that? Or standard error? SEM? Or something else?

If we are supposed to use standard deviation, then which type should it be? I noticed in Excel there are at least 4 different ways of finding standard deviation (STDEVP, STDEV, etc)

I would really appreciate if you could help me out here, I've checked some tutorials on the internet but I still couldn't figure it out.

Thank you very much!

Julianne.