Interpreting effect size F squared and Q squared

Frequently asked questions about PLS path modeling.
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thenotorious
PLS Junior User
Posts: 5
Joined: Wed Jan 02, 2019 4:13 pm
Real name and title: Aidin Yavari, Student

Interpreting effect size F squared and Q squared

Post by thenotorious » Sun Feb 10, 2019 12:19 pm

Hi all,

I have a model with:
1 IV
2 Mediators (serial mediation)
2 DVs
1 Moderator (between direct link IV --> DV1 and IV --> DV2)

First question about effect size: I calculated the f2 value with SmartPLS and I have found six relationships with no effect, namely: Moderator link 1, moderator link 2, mediator 1--> DV1, IV --> DV1, IV --> DV2, and IV --> Mediator 1

My question now is, what does this mean? I follow the logic of Cohen saying that 0.02, 0.15, and 0.35, respectively represent small, medium, and large effects of the exogenous variable. But how do I write about this in my thesis and does it have consequences? Important to note: the relationships that have no effect are also non-significant.

Second question about Q2.

I have determined that my Q2 values are above 0, so the predictive relevance is guaranteed. Is it necessary or recomended to also calculate q2?


Thank you very much in advance!

I attached a picture of my model.

Image

thenotorious
PLS Junior User
Posts: 5
Joined: Wed Jan 02, 2019 4:13 pm
Real name and title: Aidin Yavari, Student

Re: Interpreting effect size F squared and Q squared

Post by thenotorious » Mon Feb 11, 2019 7:23 pm

Anyone has an idea perhaps?

jmbecker
SmartPLS Developer
Posts: 971
Joined: Tue Mar 28, 2006 11:09 am
Real name and title: Dr. Jan-Michael Becker

Re: Interpreting effect size F squared and Q squared

Post by jmbecker » Wed Feb 13, 2019 3:01 pm

First:
It does mean that there is no effect. At least on average (if you are looking at the awareness effects, but have a significant interaction effect).
Btw, I would usually report it the other way: first significance (if not significant than there is no effect), second strength (i.e., effect size f²) to answer wether relation is substantial when it is significant.

Second:
That depends. I personally do not like the q² effect sizes so much, because there is a lot of controversy about how to correctly calculate them, but generally it could be interesting to look at them too.
Dr. Jan-Michael Becker, University of Cologne, SmartPLS Developer
Researchgate: https://www.researchgate.net/profile/Ja ... v=hdr_xprf
GoogleScholar: http://scholar.google.de/citations?user ... AAAJ&hl=de

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