This show how to add the lines
http://peltiertech.com/Excel/Charts/...orzSeries.html

You need three lines
=Average(rng)+3*stdev(rng)
=Average(rng)
=Average(rng)-3*stdev(rng)

best wishes
--
Bernard V Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme
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"patiencescientist" wrote in
message ...
I need to chart standard deviation in my worksheet. There needs to be 3
times the standard deviation (positive and negative) Is the average added
to
these two values
to be correct thanks in advance.