Shorthand for labeling statistical differences?
Cueball
In brief: if one has a bar graph showing some sample means and wants to indicate in a figure which means are statistically different without
too many asterisks and lines, how does one do that?
In detail: I have a bar graph of 6 sample means. The 1st and 2nd bars are statistically different from the 3rd, 4th 5th and 6th, but not
from each other. The 3rd is also different from the 5th and 6th.
Ordinarily in papers, I see statistically signifcant differences shown with a line over the two relevant bars and an asterisk indicating
that they are different. However, in this case, there would be far too many lines/asterisks for all the combinations of differences. I'd
like to know if there's a better way of conveying this fact that is also understood by the general scientific audience.
So is there a shorthand for this sort thing? Any thoughts would be appreicated!
TIA,
-Mark
David Jones
How about setting out a 6 by 6 table so that the columns or rows are alligned with your bars, depending on whether they are vertical or horizontal (preferably vertical for the sake of the arrangement?) . Then put no, one, two or three stars, depending on "significance" of the difference, in each cell. Possibly put dots on the diagonal. Add an additional set of labels for those things not already labelled for the bar plot.
David Jones
Gus Gassmann
If you want to do it pictorially, you can arrange the means on a
number line. Draw a vertical line between means 2 and 3 to indicate
that 1 and 2 are different from the rest. Draw some kind of bracket,
loop or whatever you can do easily over 1 and 2, 3 and 4, and again
over 4, 5 and 6 to indicate that they are not statistically different.
This should be generalizable for rather a large number of comparisons.
jos jansen
Calculate a LSD = least significant difference between two means and
draw a piece of line of LSD-length in your graph; forget about the
hocus-pocus around multiple comparisons.
Richard Ulrich
> I have a stats question. Or more like a stats representation question.
>
> In brief: if one has a bar graph showing some sample means and wants to indicate in a figure which means are statistically different without
> too many asterisks and lines, how does one do that?
>
> In detail: I have a bar graph of 6 sample means. The 1st and 2nd bars are statistically different from the 3rd, 4th 5th and 6th, but not
> from each other. The 3rd is also different from the 5th and 6th.
[snip]
That sounds pretty concise to me. A footnote.
--
Rich Ulrich, wpi...@pitt.edu
http://www.pitt.edu/~wpilib/index.html