Date: Mon, 5 Sep 2005 15:19:24 -0400
Reply-To: "Frank J. Gallo" <email@example.com>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: "Frank J. Gallo" <firstname.lastname@example.org>
Subject: ANOVA and Post-hoc Tests
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Looking for some help on interpreting contradictions found in an ANOVA run
with TukeyHSD follow-up. The F-test indicates significant differences among
Sum of Squares
Levene = 5.168, p=.002, the null hypothesis that the error variance of the
dependent variable is equal across groups suggests no.
But, post-hoc comparisons show no significant differences among groups.
And, the homogenous subsets table identifies one set (4 groups, p=.143)
indicating that the means of the subgroups are not significantly different
from each other.
I do have unequal sample sizes: 23, 42, 30, 48. The run used the harmonic
mean (32.934), so I am aware that the Type 1 error level is not guaranteed.
Is this what I am seeing? That is, the p-value for the F-test is
underestimated and it should be larger. This is my first experience with
this kind of situation.
Yours thoughts are greatly appreciated.