Effect size for mediation
Maria
Dear Ned,
please allow me a question, again: Could you tell me, what kind of effect size measure you have implemented to calculate the effect size of the (total) indirect effects respc. the formula?
Thank you very very much,
kind regards,
Maria
Ned Kock
Hi Maria.
It is Cohen’s f-squared – see the User Manual for the reference.
Ned
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Maria Daskalakis
Thanks again,
best regards,
Maria
-- Dipl.-Oec. Maria Daskalakis Universität Kassel - University of Kassel FB Wirtschaftswissenschaften - Faculty of Economics Fachgebiet Umwelt- und Verhaltensökonomik - Environmental Economics and Behavioral Economics Nora-Platiel-Str. 4 34109 Kassel fon +49 (0)561-804-3052 fax +49 (0)561 804-3882 mailto:daska...@wirtschaft.uni-kassel.de http://www.ivwl.uni-kassel.de/beckenbach/mitarbeiter/daskalakis.html Projekt "Eine akteursbasierte dynamische Analyse und Bewertung von umweltpolitischen Instrumenten am Beispiel des Immissionsschutzes - Ein Beitrag zur Nachhaltigkeitsgovernance" (DABEI) Project "Agent-based dynamic analysis and evaluation of economic instruments: the example of immission control - A contribution to the governance of sustainability" http://www.uni-kassel.de/beckenbach/index.php?option=com_content&view=article&id=43&Itemid=5&lang=de Projekt "Innovative Ansätze zur Verbesserung der Anreizwirkungen umweltpolitischer Instrumente: Bestandsaufnahme innovativer Erklärungsansätze" Project "Innovative approaches for improving the incentives of environmental instruments: state of the art" http://www.uni-kassel.de/beckenbach/index.php?option=com_content&view=article&id=61&Itemid=5&lang=de Projekt "Gender & Gründungsinteressen: Vorschläge für eine gendersensible Entrepreneurship Education an der Universität Kassel" Project "Gender & Selfemployment: Proposals for a gender-sensitiv entrepreneurship education at the University of Kassel" http://www.uni-kassel.de/beckenbach/index.php?option=com_content&view=article&id=62&Itemid=5&lang=de Projekt "Sidestep" (Studentische Ideen Stärken die eigenen Potentiale); Eine Untersuchung zur den unternehmerischen Potentialen von Studierenden Project "Sidestep" - Exploring the entrepreneurial potential of students http://www.uni-kassel.de/beckenbach/index.php?option=com_content&view=article&id=56&Itemid=5&lang=de Diese E-Mail könnte vertrauliche und/oder rechtlich geschützte Informationen enthalten. Diese Informationen sind ausschließlich für die bezeichnete/-n Person/-en oder Einrichtung/-en bestimmt. Sollten Sie nicht der für diese E-Mail bestimmte Adressat sein, ist Ihnen jede Veröffentlichung, Vervielfältigung oder Weitergabe untersagt. Haben Sie diese E-Mail irrtümlich erhalten, bitte ich Sie, mich darüber in Kenntnis zu setzen, die E-Mail zurückzusenden und Ihr Exemplar zu vernichten.
Ned Kock
Hi Maria.
Following Cohen’s original formulation, the effect size of an indirect effect of variable A on B is the change in R-squared induced by A on B associated with the indirect effect.
It is not a product of path coefficients. The more complex the set of paths connecting A and B, the more complex becomes the calculation of the effect size for indirect (and total) effects.
Btw, if you need to isolate a particular indirect effect when there is more than one path with N segments, and thus obtain its effect size, you can use a procedure similar to the one described in the clip linked below.
Just be careful not to bias the effect size upwards by removing path segments that would tend to reduce it.
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Maria Daskalakis
Hi Ned,
thank you very much! It is now clear to me - I think this is a
very good,
simple and straightforward way to estimate the effect size, as
what we are really
interested in is the change in R2.
I was looking at some papers the last two days concerning the
question, which
effect size measure to take for estimating the effect sizes of
indirect effects.
There seems to be no agreement yet, and some effect sizes, as
the ones emphasized
in Preacher/Kelly 2011 are rather complicated. Preacher/Kelly
also state, that
"Such an effect [the indirect effect] is complex because it is
the
product of (here) two regression coefficients and does not fit
conveniently
into the framework of existing effect sizes." (p. 95; with
reference to Cohen, albeit
to cohens d, which is anyway not useful for the given purpose).
May I ask, what you think about that statement?
Best regards,
Maria
Ned Kock
Hi Maria.
The approach used by WarpPLS to calculate indirect and total effects automatically obviates many of the techniques that propose to do that manually, such as the one proposed by Preacher & Hayes as well as various permutations and variations.
I agree that calculating effect sizes for indirect and total effects based on manual techniques using intermediate coefficients is problematic, and likely to lead to errors and unreliable results in many cases.
The multivariate definition of effect size due to a variable A (adopted by Cohen), which is the variation in R-squared due to that variable in the context of a multivariate model, is widely accepted.
Btw, within Cohen’s framework for effect size calculation, the d coefficient is not used at all in WarpPLS.