Posted by
Omar Farook on
Jan 16, 2007; 8:14am
URL: http://spssx-discussion.165.s1.nabble.com/is-it-correct-if-I-use-Mann-Whitney-U-tp1073199p1073201.html
Dear Dr. Simon,
Thanks for information.
I have two column, and each column contain 4 codes, zero = 0-9, one=10-14, two=15-20, and three=21-30.
Kindly, the definition of McNemar test talking about two related dichotomous variables, and I dont have dichotomous variables, my two variables contain 4 categories from 0 to 4 as I have mentioned above , also I dont have a "before-and-after" data.
So in this case could I use McNemar test? By the way, I have the original values also.
Many thanks.
Omar.
"Simon, Steve, PhD" <
[hidden email]> wrote: Omar writes:
> I have a 72 reading , the first 36 reading are from tooth one
> and the rest from tooth two , the readings are from 36 patient ,
> i.e. two readings per patient. The readings format are 0 , 1 , 2 ,
> and 3 , and each value representing rang, for example , 0
> representing from 0 -9. I want to test if there is a significant
> difference between the two readings of each patient. So by using
> SPSS , is it correct if I use Mann-Whitney U?
I'm not quite sure what the word "rang" means, so perhaps you can
clarify this. But I am quite certain that you do not want the
Mann-Whitney U. This statistic compares two independent groups, and your
groups are clearly related. Two teeth that come from the same mouth
share a common environment and are likely to be strongly correlated. In
fact, you're glad they are strongly correlated, because it improves the
efficiency of your analysis.
If you look at the SPSS menu for nonparametric tests, there is a choice
for "two related samples." This brings up a dialog box which offers the
Wilcoxon, Sign, and McNemar tests. I suspect you want the McNemar test.
Wilcoxon isn't going to work so well because you have a lot of ties in
your data set, and the sign test, though conceptually very simple and
with very few assumptions, just isn't quite as efficient.
If the code 0 represents a range (rang?) of values then you might be
able to gain even more efficiency by using the original values rather
than summarizing them as inside certain ranges. Without more context,
though, I can only speculate.
Finally, if your data is a single column rather than two adjacent
columns, you may need to use the restructure data wizard.
I hope this helps.
Steve Simon,
[hidden email], Standard Disclaimer
My niece (Bachelor's degree in Chemical Engineering
from Carnegie Mellon) is looking for a job. Any help
or leads you can provide would be greatly appreciated.
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