On 10 Jun 2001 07:27:55 -0700, [EMAIL PROTECTED] (Kelly) wrote:
> I have the gage repeatability & reproducibility(gage R&R) analysis
> done on two instruments, what hyphoses test can I use to test that the
> repeatability variance(expected sigma values of repeatability) of the
> two instruments are significantly different form each other or to say
> one has a lower variance than the other.
> Any insight will be greatly appreciated.
> Thanks in advance for your help.
I am not completely sure I understand, but I will make a guess.
There is hardly any power for comparing two ANOVAs that are
done on different samples, until you make strong assumptions
about samples being equivalent, in various regards.
If ANOVAs are on the same sample,
then a CHOW test can be used on the "improved prediction"
if one hypothesis consists of an extra d.f. of prediction.
If ANOVAs are on separate samples, I wonder if you could
compare the residual variances, by the simple variance
ratio F-test -- well, you could do it, but I don't know what arguments
should be raised against it, for your particular case.
There are criteria resembling the CHOW test that are used less
formally, for incommensurate ANOVAs (not the same predictors)
- AKAIKE and others.
If your measures are done on the same (exact) items, you
might have a paired test. Instrument A gets closer values on
<how many> of the measurements that are done.
Finally, if you can do a bunch of separate experiments, you
can test whether A or B does better in more than half of them.
--
Rich Ulrich, [EMAIL PROTECTED]
http://www.pitt.edu/~wpilib/index.html
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