[R-meta] Can we call moderators in subgroup analysis predictors?

[Viechtbauer, Wolfgang (SP)]

I think the reviewer uses the term "meta-analysis" exclusively when pooling a bunch of effects into a single weighted average. So, to him/her, it does not make sense to say that there are predictors/moderators/covariates (whatever you want to call them) in a meta-analysis. If there are predictors in the model, then the reviewer wants this to be called "meta-regression" and not "meta-analysis with predictors". I don't think the comment has anything to do with whether you use the term predictor or moderator.

Best,
Wolfgang

>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org]
>On Behalf Of Simon Harmel
>Sent: Sunday, 20 December, 2020 0:39
>To: Michael Dewey
>Cc: R meta
>Subject: Re: [R-meta] Can we call moderators in subgroup analysis
>predictors?
>
>Thank you Michael. I had the same reaction. So, this was from a reviewer
>who mentioned:
>
>"You say moderators will eventually serve as predictors in a meta-analysis,
>are you referring to meta-regression here? Moderators are not used as
>predictors in a classic meta-analysis which simply pools all the effects
>into a weighted effect size."
>
> My response was:
>
>". . . In both cases, categorical moderators/predictors act as on-and-off
>switches. I always prefer the meta-regression as it reveals the partial
>effect of one moderator controlling for other moderators. But again, in my
>context it is fine to generally use the term predictor. I think some may
>even find the term moderator confusing because in general it may denote
>some kind of interactional effect".
>
>Just wanted to make sure I'm not too far off.
>
>Thanks,
>Simon
>
>On Sat, Dec 19, 2020 at 4:32 AM Michael Dewey <lists using dewey.myzen.co.uk>
>wrote:
>
>> Dear Simon
>>
>> My immediate thought is, "Yes, why not?" but do you have some deep doubt
>> you want to share with us?
>>
>> Michael
>>
>> On 18/12/2020 22:51, Simon Harmel wrote:
>> > For clarification, I'm only concerned with categorical moderators.
>> >
>> > Thanks again,
>> > Simon
>> >
>> > On Fri, Dec 18, 2020 at 3:33 PM Simon Harmel <sim.harmel using gmail.com>
>> wrote:
>> >
>> >> Hello All,
>> >>
>> >> A quick question. In classic meta-analysis, moderators help to form
>> groups
>> >> of studies and conduct meta analysis separately in each group.
>> >>
>> >> In meta-regression, moderators are directly predictors of effect size
>> in a
>> >> regression analysis.
>> >>
>> >> But, can we still call moderators in classic meta-analysis predictors
>of
>> >> effect size?
>> >>
>> >> Thank you,
>> >> Simon