[R-meta] Random-effects meta-analyses with inverse-variance weights cannot include studies with sample sizes of two?

[Viechtbauer, Wolfgang (SP)]

I wonder what effect size / oucome measure can sensibly be computed based on two subjects. For example, for measures based on two groups (e.g., raw or standardized mean difference, risk difference, log risk/odds ratios), this would imply that there is a single subject in each group.

Best,
Wolfgang

-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On Behalf Of Patrizio Tressoldi
Sent: Friday, 02 November, 2018 15:19
To: Michael Dewey; r-sig-meta-analysis using r-project.org
Subject: Re: [R-meta] Random-effects meta-analyses with inverse-variance weights cannot include studies with sample sizes of two?

In this case the reviewer referred to the calculation of the effect size
of an individual primary study.

Patrizio

Il 02/11/2018 13:33, Michael Dewey ha scritto:
> Can you just clarify Patrizio, does the referee mean that an
> individual primary study must have a sample size greater than two or
> that your meta-analysis must include more than two primary studies?
> Either way it seems dubious to me.
>
> Michael
>
> On 02/11/2018 09:38, Patrizio Tressoldi wrote:
>> A need your advise about a referee comment: "random-effects
>> meta-analyses with
>> inverse-variance weights cannot include studies with sample sizes of
>> two".
>>
>> Is this statement correct, and if yes, why?
>>
>> Thanks
>> Patrizio
>>
>> --
>> Patrizio E. Tressoldi Ph.D.
>> Dipartimento di Psicologia Generale
>> Università di Padova
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>> https://orcid.org/0000-0002-6404-0058
>>
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