[R-meta] Subgroup analyses under the multi-level (3 level) meta-analysis model

[Saya Fujita]

Dear Professor Viechtbauer,

Thank you very much! 

Warmest regard,
Saya


On 14/03/2021, 17:45, "Viechtbauer, Wolfgang (SP)" <wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:

    Dear Saya,

    Please keep the mailing list in cc.

    One level is the reference level (namely 'Corr') and you get three contrasts with this reference level. Please see:

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

    Best,
    Wolfgang

    >-----Original Message-----
    >From: Saya Fujita [mailto:sayakaf.p using gmail.com]
    >Sent: Sunday, 14 March, 2021 17:43
    >To: Viechtbauer, Wolfgang (SP)
    >Subject: Re: Subgroup analyses under the multi-level (3 level) meta-analysis model
    >
    >Dear Professor Viechtbauer,
    >
    >Thank you very much for your prompt response!
    >
    >I ran the code using my original variables "Metrics" as factors.
    >I can see it has 4 levels, but my regression results only show 3 factors.
    >I am wondering why?
    >
    >The Metrics has 4 levels (Coupling, Flow, Graph, Corr) as seen below:
    >
    >> str(multi.data$Metrics)
    > Factor w/ 4 levels "Corr","Coupling",..: 1 1 1 1 1 1 1 1 1 1 ...
    >
    >Here's my codes:
    >
    >subEEG.Metrics<-rma.mv(y,
    >                   v,
    >                   random = ~ 1 | PaperID/AnalysisID,
    >                   tdist = TRUE,
    >                   data = multi.data,
    >                   method = "REML",
    >                   mods = ~ Metrics)
    >
    >And the results are:
    >
    >Model Results:
    >
    >                 estimate      se     tval    pval    ci.lb   ci.ub
    >intrcpt            0.8795  0.2458   3.5788  0.0005   0.3933  1.3658  ***
    >MetricsCoupling   -0.1432  0.2982  -0.4804  0.6318  -0.7332  0.4468
    >MetricsFlow        0.1238  0.4307   0.2876  0.7742  -0.7283  0.9760
    >MetricsGraph      -0.0084  0.4257  -0.0196  0.9844  -0.8506  0.8339
    >
    >If you could kindly let me know whether I am doing something wrong, I would be so
    >appretiative!
    >
    >Thank you very much again!
    >
    >Warmest regards,
    >Saya
    >
    >On 14/03/2021, 15:52, "Viechtbauer, Wolfgang (SP)"
    ><wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
    >
    >    Dear Saya,
    >
    >    You do not need to create these 'dummy variables' yourself. Just declare the
    >variable that distinguishes the various subgroups as a factor and include it as a
    >predictor via 'mods'. You also might want to read this:
    >
    >    https://www.metafor-project.org/doku.php/tips:models_with_or_without_intercept
    >
    >    It's not focused on rma.mv() (i.e., it uses a simpler model), but the same
    >principles apply.
    >
    >    Best,
    >    Wolfgang
    >
    >    >-----Original Message-----
    >    >From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org]
    >On
    >    >Behalf Of Saya Fujita
    >    >Sent: Sunday, 14 March, 2021 16:24
    >    >To: R-sig-meta-analysis using r-project.org
    >    >Subject: [R-meta] Subgroup analyses under the multi-level (3 level) meta-
    >analysis
    >    >model
    >    >
    >    >Dear All,
    >    >
    >    >I am conducting a 3-level multi-analysis, following this Bookdown.
    >    >https://bookdown.org/MathiasHarrer/Doing_Meta_Analysis_in_R/mlma.html
    >    >
    >    >I would like to run some sub-group analyses under this 3 level structure, and
    >I
    >    >can see in this bookdown (chapter 12.1) that if I use rma.mv function in
    >metafor,
    >    >we need to create two variables/columns for each subgroup level. In the
    >example in
    >    >this book down, the number of sub-groups was two: peer-review, dissertation,
    >so it
    >    >makes sense that they coded 1 (yes) or 0 (no).
    >    >
    >    >In my data I have more than two subgroups, and I wonder how I should input
    >the
    >    >data. I thought, if I have 4 subgroups for instance, I’d create 4 columns and
    >code
    >    >0 or 1 in each column, but that would group 3 different levels as 0 in one
    >column,
    >    >and specifying one variable/column as a moderator in rma.mv using
    >    >the mods parameter would compare one subgroup with the other three subgroups
    >–
    >    >which is not what I want to do. Hope this makes sense!
    >    >I wonder if anyone here has done a subgroup analysis for multiple subgroup
    >    >comparisons, maintaining the 3 level structure of a multi-level meta-
    >analysis?
    >    >Could I ask how you did the analysis?
    >    >
    >    >Thank you very much in advance, and I apologise if it’s a very simple/naïve
    >    >question!
    >    >
    >    >Many thanks,
    >    >Saya
    >    >
    >    >*********
    >    >Sayaka Kidby (Fujita)| PhD candidate, Marie Skłodowska-Curie Early Career
    >    >Researcher [she/her]
    >    >Psychology | Lancaster University
    >    >s.kidby using lancaster.ac.uk
    >    >www.lancaster.ac.uk