Posted by
Hector Maletta on
Mar 23, 2007; 11:19pm
URL: http://spssx-discussion.165.s1.nabble.com/Levene-test-with-large-sample-tp1074661p1074665.html
The main point, I think, is that your conclusion stands either under
the equal variances or the unequal variances hypotheses. This is, of course,
in part due to the fact that your sample is large. And that is a good thing.
Now, to report your results you may choose one hypothesis or another
about the equality of variances (both leading to the same substantive
conclusion). Since (at your sample size) the variances observed in the
groups lend credence to the different-variances hypothesis, i.e. the
difference in variances is statistically significant, you may want to use
that one for reporting purposes.
Finding different variances is not altogether surprising. I imagine
your results do not come from any randomized experimental design, but from
some observational study, so it would be mere fluke that your groups show
equal variances. One should rather EXPECT different variances (as one would
rather expect different group sizes) for the various groups.
Hector
-----Mensaje original-----
De: SPSSX(r) Discussion [mailto:
[hidden email]] En nombre de
Stephen Salbod
Enviado el: 23 March 2007 23:04
Para:
[hidden email]
Asunto: Levene test with large sample
Good Evening Everyone,
I hope someone will guide me around this simple problem that fell in
front
of me today.
Which t test do I want to report?
I have two groups:
Group1 n= 1,512 M=2.5668 SD1=.80339
Group2 n= 273 M=2.3187 SD2=.96877
Levene's Test for Equality of Variance F= 27.531, p<.0001.
1) Equal Variances Assumed t(1783) = 4.542, p <.001.
2) Equal Variances NOT Assumed t(342.79) = 3.991.
The large N has created a statistically significance difference out
of a
trivial difference; furthermore, the variances between the groups
are
statistically different.
Can Levene's result be ignored because of the large sample or is it
recommended that I report t test #2?
I would appreciate any suggestions and, if possible, references on
this
problem.
I thank you in advance.
Stephen Salbod, Pace University