Peggy -

When Brand X computes the average, it could also compute the standard deviation.
These could be placed in an adjacent worksheet range, and used as the custom +/-
error bar values. For more detailed instruction, look he

http://peltiertech.com/Excel/ChartsHowTo/ErrorBars.html

- Jon
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Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______

Peggy wrote:

I have graphed some data where each data point is the
average of 5 replicates. I did the statistics in a program
other than Excel. In my Excel graph, under 'Format Data
Series' I have never understood how to add y error bars.
It seems to me the data set that generated the graph
doesn't have enough information to do this. It doesn't
know the value of each of the five replicates, just the
average.
What am I missing?