[R-meta] How to Get PIs for Moderator Analyses

[Tori Peña]

Hi Wolfgang,

Thank you for clarifying!  I apologize for the misunderstanding.

I'm trying to use the newmods argument just now but am still confused.  I
tried entering the moderator name which did not work.  I also checked the
website <https://wviechtb.github.io/metafor/reference/predict.rma.html>,
but I don't see a way to get the PIs for the output of the moderator models
(see attached).  What exactly do I specify in the 'newmods' argument?

Thanks,
Tori

On Fri, Jun 23, 2023 at 7:53 AM Viechtbauer, Wolfgang (NP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:

> Dear Tori,
>
> The profile() function is not for getting PIs. You are misunderstanding
> what Michael was suggesting -- he was suggesting to use profile() to check
> if the variance components are identifiable by examining the profile
> likelihood plots. And predict() works just fine for getting PIs. Like I
> wrote, you have to use the 'newmods' argument in predict() to specify for
> which combination of moderator values you want to obtain a predicted
> effects (and the corresponding CI and PI).
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: R-sig-meta-analysis [mailto:
> r-sig-meta-analysis-bounces using r-project.org] On
> >Behalf Of Tori Peña via R-sig-meta-analysis
> >Sent: Thursday, 22 June, 2023 19:37
> >To: R Special Interest Group for Meta-Analysis
> >Cc: Tori Peña
> >Subject: Re: [R-meta] How to Get PIs for Moderator Analyses
> >
> >Thanks, all!
> >
> >Unfortunately, the profile() function did not yield PIs for our moderator
> >analyses.  Are there other ways to get the PIs for rma.mv models since
> >predict() and profile() are not working?
> >
> >On Thu, Jun 15, 2023 at 12:18 PM Michael Dewey via R-sig-meta-analysis <
> >r-sig-meta-analysis using r-project.org> wrote:
> >
> >> Dear Tori
> >>
> >> Just to clarify the reasoning behind my comments I was concerned that
> >> your data may not be adequate to fit the model since you seemed to have
> >> very small random variances and little effect from the moderators.
> >>
> >> Michael
> >>
> >> On 14/06/2023 10:22, Viechtbauer, Wolfgang (NP) via R-sig-meta-analysis
> >> wrote:
> >> > Michael means using the profile() function.
> >> >
> >> > This aside, if you use predict(<model>), then it will compute
> >> predicted/fitted values based on the model matrix (and corresponding
> >> CIs/PIs). If you want predicted values for particular combinations of
> >> moderator values, then you have to specify the 'newmods' argument.
> >> >
> >> > Best,
> >> > Wolfgang
> >> >
> >> >> -----Original Message-----
> >> >> From: R-sig-meta-analysis [mailto:
> >> r-sig-meta-analysis-bounces using r-project.org] On
> >> >> Behalf Of Tori Peña via R-sig-meta-analysis
> >> >> Sent: Tuesday, 13 June, 2023 19:51
> >> >> To: Michael Dewey
> >> >> Cc: Tori Peña; R Special Interest Group for Meta-Analysis
> >> >> Subject: Re: [R-meta] How to Get PIs for Moderator Analyses
> >> >>
> >> >> Hi Michael,
> >> >>
> >> >> Thanks for your response!  What do you mean by profiling the
> variance?
> >> >> Yes, some of my moderators had virtually no effect in our models.  I
> >> have
> >> >> the issue with the PI being displayed for each data point in the
> model
> >> >> instead of the PI for the model across all the moderators,
> >> unfortunately.
> >> >>
> >> >> On Tue, Jun 6, 2023 at 12:20 PM Michael Dewey <
> lists using dewey.myzen.co.uk>
> >> >> wrote:
> >> >>
> >> >>> Dear Tori
> >> >>>
> >> >>> It might help to know exactly why you think the ouput is incorrect
> but
> >> I
> >> >>> notice that (a) your random effects seem to have very small
> variances
> >> >>> (have you tried profiling them?) (b) your moderator does not seem to
> >> >>> have much effect either.
> >> >>>
> >> >>> Michael
> >> >>>
> >> >>> On 06/06/2023 16:59, Tori Peña via R-sig-meta-analysis wrote:
> >> >>>> Hello Listserv -
> >> >>>>
> >> >>>> I wanted to know if folks know of a way to get prediction intervals
> >> for
> >> >>>> moderator analyses!  I tried the predict() function but the output
> >> looks
> >> >>>> incorrect.  I attached a screenshot below of the code plus a part
> of
> >> the
> >> >>>> output.
> >> >>>>
> >> >>>> Thanks in advance!
> >> >>>>
> >> >>>> --
> >> >>>> *Tori Peña, Ph.D. *(she/her/ella)
> >> >>>> Cognitive Psychology
> >> >>>> Dept. of Psychology
> >> >>>> Stony Brook University
> >> >>>> Stony Brook, NY 11790-2500
> >> >>>> Stony Brook University logo
>

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