JE McGimpsey wrote...
I'm not sure why you're not using XL's built in AVERAGE() formula. I
suppose you could use a wrapper function:

Public Function Mean(vArr As Variant)
Mean = Application.Average(vArr)
End Function

but I don't see the point.
....

And all to calculate relative standard deviation, which is just

=100*STDEV(rng)/AVERAGE(rng)

or, for older pathological versions of Excel,

=100*SQRT(DEVSQ(rng)/(COUNT(rng)-1))/AVERAGE(rng)

Note that it's a worthless statistic when rng could have a nonpositive
mean.