[R] How do I print predicted effect sizes in forest plot?

[Viechtbauer Wolfgang (STAT)]

The model you are fitting is a random-effects model and does not include any potential moderators/covariates. Therefore, the estimated intercept of that model is *the* estimated/predicted (average) effect and it applies to each study. That is why the predict function also just gives you that value. That value is also included in the forest plot (at the bottom). The predicted (average) effect will no longer be the same for each study only if you include covariates in the model.

Best,
Wolfgang

--   
Wolfgang Viechtbauer, Ph.D., Statistician   
Department of Psychiatry and Psychology   
School for Mental Health and Neuroscience   
Faculty of Health, Medicine, and Life Sciences   
Maastricht University, P.O. Box 616 (VIJV1)   
6200 MD Maastricht, The Netherlands   
+31 (43) 388-4170 | http://www.wvbauer.com   

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Alma Wilflinger
> Sent: Thursday, December 05, 2013 22:06
> To: R help <r-help at r-project.org>
> Subject: [R] How do I print predicted effect sizes in forest plot?
> 
> Hi,
> 
> I am struggling a bit with creating a forest plot containing the predicted
> effect size. As seen in other studies these effect sizes are shown per
> study usually as a light grey diamond - which is what I want to achieve.
> 
> The calls I use are:
> iat_result = rma(yi=Mean, vi=Variance_rounded, ni=N, sei=Std_error,
> slab=Study_Name, subset=(Country == "AUT"), data=cma_iat, method="HS")
> 
> summary.rma(iat_result)
> 
> 
> #not sure how to use it or if needed
> #predict(iat_result)
> 
> forest(iat_result)
> 
> 
> At the end I am getting the forest plot as is without the predicted
> values.
> 
> I am not sure if I need the predict function and how to use it? - the
> predict function deliveres the same values as already computed in the rma
> object.
> 
> 
> I checked the manual for package metafor but was not able to find out how
> to print the predicted values per study.
> 
> 
> kind regards, Alma
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