On Tue, 11 Jan 2000, Glenn Gee wrote:
> I have a question in regards to which test statistic to use. Example:
> my problem is a test of glue "A" vs glue "B". I have a test that just
> determines if glue "A" remains stuck to the surface or not.
I cannot imagine being interested in whether glue "A" (or "B") remains
stuck to the surface or not. Surely one's interest is in whether two
things remain stuck together when glue "A" is used as an adhesive, not
in whether glue "A" merely sticks to one of them. In fact, I have some
difficulty imagining a physical procedure for determining whether glue
"A" remains stuck to a surface: it's much easier to imagine a setup
testing whether two objects remain stuck together.
> The test does not have any other measurements. It holds or does not
> hold.
There surely are other measurements, even if you choose to ignore them.
Whether a glue holds or does not (however one has chosen to define
"hold", which is not stated) depends on (inter alia) the materials of
which the adhering surfaces are made, the distance between the surfaces,
the roughness of the surfaces, the force applied in attempting to detach
one surface from the other, and the direction of that force (e.g.,
whether parallel to the surfaces, so that one is testing the shear
strength of the set glue, or normal to the surfaces, so that one is
testing its tensile strength). Presumably all of these variables are
being held constant in the experiment you allude to. If not, no
conclusions can be drawn, however many samples you test.
> If I test 5 samples of glue "A" against 5 samples of glue "B" with
> the following results:
> glue "A" held 4 times, glue "B" held 2 times.
> Can I make a valid decision?
Depends in part on how you mean "valid".
You cannot make a very reliable one.
> Do I need more samples?
Yes.
> Suggestions?
Some are hinted at above. Others might be possible, but not
with the current lack of detail and definition.
-- DFB.
------------------------------------------------------------------------
Donald F. Burrill [EMAIL PROTECTED]
348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED]
MSC #29, Plymouth, NH 03264 603-535-2597
184 Nashua Road, Bedford, NH 03110 603-471-7128
