Errata....

I wrote:
the median deviation is defined as the average of the absolute deviations
from the median. [....] You can compute it with the following array
formula[*]:
=SUM(ABS(A2:A100-A1:A99))/100

Brain fart! I mean:

=SUM(ABS(A1:A100-MEDIAN(A1:A100)))/100

And note that for "/100", 100 relates to the number of data points (100),
not a constant like "percent".


----- original message -----

"Joe User" joeu2004 wrote in message
...
"Omics" wrote:
Hi, Anybody can tell me which function or formula
should I use in excel to calculate the median
standard deviation?

You will need to be more careful with your terminology if you want a
meaningful answer.

First, are you referring to the median or the mean (arithmetic average)?

The median is the middle value of the data. The mean is the average of
the
data. For example, if the data are 1, 4 and 5, 4 is the median, whereas
the
mean is about 3.33.

Note that the standard deviation (emphasis on "standard") is defined as a
deviation from the mean, not the median.

I 'spose that you could substitute the median for the mean in the standard
deviation formula. (See the STDEVP help page.) But then it would not be
"standard" ;-). And the usefulness of such a measure is unclear.

On the other hand, the median deviation is defined as the average of the
absolute deviations from the median.

To my knowledge, there is no Excel formula for that. You can compute it
with the following array formula[*]:

=SUM(ABS(A2:A100-A1:A99))/100

[*] Enter an array formula by pressing ctrl+shift+Enter instead of just
Enter. In the Formula Bar, you will see curly braces around the entire
formula, viz. {=formula}. You cannot type the curly braces yourself; that
is
just Excel's way of denoting an array formula. If you make a mistake,
select
the cell, press F2, edit as needed, then press ctrl+shift-Enter.

Lastly, if you mean that you have a set of standard deviations, and you
want
to calculate their median, you could use =MEDIAN(A1:A10). But again, the
usefulness of such a measure is unclear.