standard deviation

[Giulio Defeudis]

hello dudes,

i am trying to graph say shoe sales by week, i'd like to
include a trendline and the trendline plus and minus the
standard deviation.

is it possible to do this within excel, powerpoint or the
graph software that comes with office 97?

i know i can include the trendline but not sure about
plotting the trendline with the standard deviation.

thanks a lot
giulio

 

[Jon Peltier]

Giulio -

Also see my answer to your earlier post.

Indicating the error in a trendline is trickier than just plotting a
standard deviation, because the error can be error in position
(intercept) and in slope. When the scatter band is indicated around a
trendline, it is generally wider at the ends, because of pivoting of the
trendline due to slope error.

I don't need my statistics books in my current situation, so I can't
post anything, but you could try searching the google group archives.
Seems to me Jerry Lewis has posted the formula you're interested in,
within the past couple of months.

- Jon