[R-meta] variance of predicted effect sizes
Viechtbauer, Wolfgang (SP)
wolfg@ng@viechtb@uer @ending from m@@@trichtuniver@ity@nl
Fri Nov 16 15:55:59 CET 2018
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In metafor, predict() gives standard errors of predicted values, labeled 'se' in the output and element 'se' in the object returned by predict().
Best,
Wolfgang
-----Original Message-----
From: Crean, Hugh [mailto:hugh_crean using URMC.Rochester.edu]
Sent: Friday, 16 November, 2018 15:52
To: Viechtbauer, Wolfgang (SP)
Subject: Re: variance of predicted effect sizes
Hi Wolfgang,
Yes, that is it exactly. What I cannot find from your response below is "...Then you would use the squared standard error of the predicted value (from the meta-regression model) as the sampling variance of the control group estimate...." I cannot find (or figure a sensible formula for computign) the standard error of the predicted value.
Best,
Hugh
Hugh F. Crean, Ph.D.
University of Rochester
School of Nursing
Helen Wood Hall 4.W111
601 Elmwood Avenue
Box SON
Rochester, New York 14642
(585) 276-5575
(585) 273-1258 (fax)
Hugh_Crean using urmc.rochester.edu
________________________________________
From: Viechtbauer, Wolfgang (SP) <wolfgang.viechtbauer using maastrichtuniversity.nl>
Sent: Friday, November 16, 2018 9:46 AM
To: Crean, Hugh
Subject: RE: variance of predicted effect sizes
Dear Hugh,
It sounds to me that you want to do something like Becker (1988) describes in section 5.2. Then you would use the squared standard error of the predicted value (from the meta-regression model) as the sampling variance of the control group estimate of the standardized mean change.
There is an additional complication that there is then a dependency between the effect sizes (i.e., the difference in the standardized mean change between the treatment and control group) for studies with both treatment and control groups and effect sizes for studies with just a treatment group (and also between the effect sizes from studies with treatment groups only). These covariances can be computed as described in 5.2 and would need to be put into the 'V' matrix of rma.mv() (if you intend to use metafor). Actually implemting this would require a bit of work though. Showing how to do this with metafor would be a nice little exercise/project for a motivated student.
Best,
Wolfgang
-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On Behalf Of Crean, Hugh
Sent: Sunday, 11 November, 2018 23:22
To: 'r-sig-meta-analysis using r-project.org'
Subject: [R-meta] variance of predicted effect sizes
Hello,
Colleagues and myself are working on a meta-analysis of sleep interventions. Many of the studies are only single arm pre-post studies and we are following the advice of Becker (1988) and Morris and DeShon (2002) to impute missing control group effect sizes. We are planning on using meta regression to compute predicted effect sizes for those studies missing control information. However, I cannot quite figure how to compute and/or get the standard error for this estimate. Would one run a simple meta- analysis on the predicted scores for those with the data and use the provided se (and variance)?
Thanks in advance,
Hugh
Hugh F. Crean, Ph.D.
School of Nursing
University of Rochester
601 Elmwood Avenue
Rochester, New York 14620
(585) 276-5575
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