Re: 95% significance test

Posted by Bruce Weaver on
URL: http://spssx-discussion.165.s1.nabble.com/95-significance-test-tp5717562p5717581.html

That's what I was thinking too.  But then I tried the following example:

GET FILE='C:\SPSSdata\1991 U.S. General Social Survey.sav'.

ONEWAY age BY region
  /MISSING ANALYSIS
  /POSTHOC=SCHEFFE BONFERRONI ALPHA(0.05).


For every pair-wise contrast, the Scheffé p-value is lower than the Bonferroni p-value:  .257 < .298; .152 < .157; .006 < .004.  If Scheffé's method is more conservative, it should have higher p-values.

But doing this example has also raised another question:  Can SPSS even do complex contrasts using Scheffé's method?  If so, how to do it is not immediately obvious.  Checking the Scheffé box in the post-hoc dialog just gives all pair-wise contrasts.

Swank, Paul R wrote

Actually, Scheffe is even more conservative than Bonferroni since it controls for all possiblle comparisons, not just pairwise.

 Dr. Paul R. Swank, Professor
Health Promotion and Behavioral Sciences
School of Public Health
University of Texas Health Science Center Houston


-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of David Marso
Sent: Tuesday, January 22, 2013 10:28 AM
To: [hidden email]
Subject: Re: 95% significance test

Indeed!
In fact Bonferroni is very (the most) conservative approach to multiple comparisons.
In your case where k=4 the effective level of significance for each comparison would be .05/4 = .0125 .


mils wrote
> Wow, thanks David, I wasn't aware that the Bonferroni adjust will make
> such a difference.
>
> Thanks,
>
> mils





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