**=========================================================================
****Date:** Wed, 19 Jul 2006 10:13:55 -0700
**Reply-To:** Dale Glaser <glaserconsult@sbcglobal.net>
**Sender:** "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
**From:** Dale Glaser <glaserconsult@sbcglobal.net>
**Subject:** Re: effect size: eta-squared vs partial eta-squared
**In-Reply-To:** <957C8A78DD5B6D42B7D33DBAB78CDC2F9ADCFB@dc2ex01.air.org>
**Content-Type:** text/plain; charset=iso-8859-1
Enis, in Keppel and Wickens (2004) the authors make a rather compelling argument against the R^2 effect size as reported in SPSS (i.e, SSa/SStotal) as opposed to omega squared, using their notation on page 164: (SSa - (a -1)MS s/a)/(SStotal + MS s/a)..they comment that omega squared "takes the sampling variability into account and so is most relevant to the population you are studying" (p. 167) and that, in their opinion, r^2 (which statistically can be shown) tends to inflate the variation accounted for.....however, SPSS does not report omega squared so one would need to hand calculate this estimate

Keppel, G., & Wickens, T. D. (2004). Design and analysis. (4th Ed.). Upper Saddle River, NJ: Pearson.

"Dogan, Enis" <edogan@air.org> wrote:
Thanks to all who replied to my question.
Any comments on the relationship between partial-eta squared and partial
R squared?
Also eta-squared looks to me like a part R squared.
Any thoughts?

Enis

-----Original Message-----
From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of
Nicholas J.S. Gibson
Sent: Wednesday, July 19, 2006 12:37 PM
To: SPSSX-L@LISTSERV.UGA.EDU
Subject: Re: effect size: eta-squared vs partial eta-squared

A quick search on "eta" in the archives will confirm that some variant
of
this question comes up pretty frequently! Unfortunately SPSS still has
no
capability to report total eta-squared values or the SS values needed to

calculate total eta-squared values for mixed-model ANOVAs by hand
(unless
this functionality has since been added to SPSS 14/15). When Kyle Weeks
last commented on this (Jan 2003 -- see
http://www.listserv.uga.edu/cgi-bin/wa?A2=ind0301&L=spssx-l&P=R2708&m=24
876
) he said this feature was on the "wish list" but I don't know if it has

since become a reality. If someone knows of development or planned
development on this it would be useful to know about it.

Reporting partial eta-squared values would indeed be misleading given
that
when summed they can exceed 1. Unfortunately without SPSS reporting
total
eta-squared values it is likely that researchers do erroneously report
partial values.

Other articles on this include:

Timothy R. Levine & Craig R. Hullett. (2002). Eta squared, partial eta

squared, and misreporting of effect size in communication research.
Human
Communication Research, 28, 612-625.

Pierce, C. A., Block, R. A., & Aguinis, H. (2004). Cautionary note on
reporting eta-squared values from multifactor ANOVA designs. Educational

and Psychological Measurement, 64, 916-924.
http://www.montana.edu/wwwpy/Block/papers/Pierce,Block,&Aguinas-2004.pdf

Nicholas Gibson

--
Nicholas J.S. Gibson, Ph.D.
Psychology and Religion Research Group
Faculty of Divinity, University of Cambridge
West Road, Cambridge, CB3 9BS, UK

tel +44 (0)1223 763010 * mob +44 (0)7970 757524 * fax +44 (0)1223 763003
http://www.divinity.cam.ac.uk/pcp/personnel/nicholas.html

> Date: Tue, 18 Jul 2006 12:01:26 -0500
> From: "Alexander J. Shackman"
>
> see also
>
> http://web.uccs.edu/lbecker/Psy590/es.htm
> and
> http://web.uccs.edu/lbecker/SPSS/glm_effectsize.htm
>
> On 7/18/06, Dogan, Enis wrote:
> >
> > Dear all
> >
> >
> >
> > SPSS reports partial et-sq as opposed to eta-squared.
> >
> > I found in the literature the rule thumb for eta-squared as small
> > (0.01), medium (0.06), and large (0.14) (Cohen, 1988).
> >
> > Does this apply to partial eta-squared as well?
> >
> > Also, the definition of eta-squared gives me the idea that it is no
> > different than what some of us call partial R squared.
> >
> > Am I right?
> >
> >
> >
> > There is rumor out there that "researchers erroneously report
partial
> > eta-squared values as representing classical eta-squared values"
> >
> > http://carbon.cudenver.edu/~haguinis/APMinpress.pdf
> >
> >
> >
> > Any value in this argument?
> >
> >
> >
> > Thanx
> >
> >
> >
> > Enis
> >
> >
> >
>
>

Dale Glaser, Ph.D.
Principal--Glaser Consulting
Lecturer--SDSU/USD/CSUSM/AIU
4003 Goldfinch St, Suite G
San Diego, CA 92103
phone: 619-220-0602
fax: 619-220-0412
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