Re: one way anova overall significant, but dunnett post hoc has no single significant group?

Posted by Rich Ulrich on Oct 19, 2012; 5:10am
URL: http://spssx-discussion.165.s1.nabble.com/one-way-anova-overall-significant-but-dunnett-post-hoc-has-no-single-significant-group-tp5715709p5715761.html

I wasn't complaining.  I was just pointing to the
direction that has been useful to me.  (Mostly, it
has been useful in teaching people about post-hoc
testing.)

--
Rich Ulrich

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From: [hidden email]
To: [hidden email]; [hidden email]
Date: Thu, 18 Oct 2012 19:25:58 -0500
Subject: RE: one way anova overall significant, but dunnett post hoc has no single significant group?

IIRC, the theorem is if and only if, that is, it does work both ways.

 

Dr. Paul R. Swank, Professor

Health Promotion and Behavioral Sciences

School of Public Health

University of Texas Health Science Center Houston

 

From: Rich Ulrich [mailto:[hidden email]]
Sent: Thursday, October 18, 2012 6:05 PM
To: Swank, Paul R; SPSS list
Subject: RE: one way anova overall significant, but dunnett post hoc has no single significant group?

 

I've always thought of the Scheffe procedure in the opposite
direction.

That is:  It sets a high standard for the individual contrast,
so that if there is *any* contrast that is significant, then the
omnibus test has to be.  (Basically, the contrast will account
for the full Sum of Squares needed for the overall test and d.f.)

--
Rich Ulrich

> Date: Thu, 18 Oct 2012 17:22:33 -0500
> From: [hidden email]
> Subject: Re: one way anova overall significant, but dunnett post hoc has no single significant group?
> To: [hidden email]
>
> There is only one post-test comparison procedure that guarantees a significant result if you have a significant omnibus test and that is Scheffe. It, however, controls for all comparisons, including complex (ie. more than two means compared like (m1 + m2)/2 - m3 = 0).
>
>
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