[R-meta] Compiling different design in the same met-analysis

[Viechtbauer, Wolfgang (SP)]

Agree, but I also want to point to this:

https://www.metafor-project.org/doku.php/tips:computing_adjusted_effects

It discusses the concept of computing adjusted effects, which may be what you are looking for, Gladys. However, as noted at the end, some may question the usefulness and interpretability of such an estimate.

Best,
Wolfgang

>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On
>Behalf Of Dr. Gerta Rücker
>Sent: Monday, 03 May, 2021 20:09
>To: Gladys Barragan-Jason
>Cc: R meta
>Subject: Re: [R-meta] Compiling different design in the same met-analysis
>
>Hi Gladys,
>
>You may pool all effects in a meta-analysis, using "design" as a
>moderator. In meta-analysis, this is called a subgroup analysis (for
>example by Cochrane). You then get both within-subgroup effects and a
>pooled effect, and also a test of treatment--design interaction, that
>says whether the treatment effect is different between designs. Thus you
>have all what you are interested in. However, in your interpretation you
>have to account for the different character of the studies: In a
>two-group parallel design, if it is randomized (you did not mention
>whether it is), you can expect an unbiased estimate of the treatment
>effect. In a pre-post design, you must expect all kinds of biases (to
>mention only regression to the mean) and also, as Michael said,
>different variation. Therefore you have to interpret results with caution.
>
>Best, Gerta
>
>Am 03.05.2021 um 19:42 schrieb Gladys Barragan-Jason:
>> Hi Gerta and Michael,
>> I am not sure to understand. I am not saying the the effect size are
>> different. They are comparable but of course differ in term of ci
>> since the number of studies, participants are different. I would like
>> to know whether we can make obtain an overall effect size while
>> controlling for design. So maybe the answer is no.
>> Thanks
>> Gladys