[R-meta] How to Get PIs for Moderator Analyses
You need to specify the values of your moderator variables for which you want to have predicted values. If you do ?predict.rma and then look at the resulting output towards the end you can find a few examples of using newmods.
On 26/06/2023 02:12, Tori Pe?a via R-sig-meta-analysis wrote:
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 at maastrichtuniversity.nl <mailto:wolfgang.viechtbauer at 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 at r-project.org
<mailto:r-sig-meta-analysis-bounces at r-project.org>] On
>Behalf Of Tori Pe?a via R-sig-meta-analysis
>Sent: Thursday, 22 June, 2023 19:37
>To: R Special Interest Group for Meta-Analysis
>Cc: Tori Pe?a
>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
<http://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 at r-project.org
<mailto:r-sig-meta-analysis at 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 at r-project.org
<mailto:r-sig-meta-analysis-bounces at r-project.org>] On
>> >> Behalf Of Tori Pe?a via R-sig-meta-analysis
>> >> Sent: Tuesday, 13 June, 2023 19:51
>> >> To: Michael Dewey
>> >> Cc: Tori Pe?a; 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 at dewey.myzen.co.uk <mailto:lists at 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 Pe?a 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 Pe?a, 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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