[R-meta] Moderator level getting removed from model

[Shannon Duncan]

Hi Wolfgang,

The table does reveal that there are no observations for the "1" coded in
Decision Aids for the 2 tridiff level.

We're essentially yes looking for a way to show this is in the reporting of
the meta analysis.

Thank!
Shannon

     0  1
  1 32 12
  2 10  0
  3 11 12



On Mon, Feb 12, 2018 at 12:56 PM, Viechtbauer Wolfgang (SP) <
wolfgang.viechtbauer at maastrichtuniversity.nl> wrote:

> Dear Shannon,
>
> Indeed, rma() will omit a coefficient from the model if it is not
> estimable. What does
>
> table(choiceaccdata$tridiff, choiceaccdata$Provides.Decision.Aids)
>
> show? I suspect this will reveal why this coefficient is not estimable.
>
> So the only thing one could print for that coefficient would be NA (not
> available). Are you looking for a way to show this?
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-
> >project.org] On Behalf Of Shannon Duncan
> >Sent: Monday, 12 February, 2018 18:23
> >To: r-sig-meta-analysis at r-project.org
> >Subject: [R-meta] Moderator level getting removed from model
> >
> >Hello,
> >
> >I have a question that I can't seem to find an answer to, hoping someone
> >here can help me out. We are running the following model:
> >
> >resalt <- metafor::rma(cohens_d, variance, mods = ~ factor(tridiff) *
> >Provides.Decision.Aids, test = "t", data = choiceaccdata)
> >
> >resalt
> >
> >## tau^2 (estimated amount of residual heterogeneity):     0.0574 (SE =
> >0.0175)
> >## tau (square root of estimated tau^2 value):             0.2395
> >## I^2 (residual heterogeneity / unaccounted variability): 67.78%
> >## H^2 (unaccounted variability / sampling variability):   3.10
> >## R^2 (amount of heterogeneity accounted for):            39.40%
> >##
> >## Test for Residual Heterogeneity:
> >## QE(df = 72) = 195.8927, p-val < .0001
> >##
> >## Test of Moderators (coefficient(s) 2:5):
> >## F(df1 = 4, df2 = 72) = 6.8504, p-val < .0001
> >##
> >## Model Results:
> >##
> >##                                          estimate      se     tval
> >pval
> >## intrcpt                                   -0.2234  0.0527  -4.2434
> ><.0001
> >## factor(tridiff)2                          -0.1642  0.1415  -1.1609
> >0.2495
> >## factor(tridiff)3                          -0.4823  0.1523  -3.1656
> >0.0023
> >## Provides.Decision.Aids                     0.2183  0.0996   2.1910
> >0.0317
> >## factor(tridiff)3:Provides.Decision.Aids    0.6595  0.2218   2.9736
> >0.0040
> >##                                            ci.lb    ci.ub
> >## intrcpt                                  -0.3284  -0.1185  ***
> >## factor(tridiff)2                         -0.4462   0.1178
> >## factor(tridiff)3                         -0.7860  -0.1786   **
> >## Provides.Decision.Aids                    0.0197   0.4169    *
> >## factor(tridiff)3:Provides.Decision.Aids   0.2174   1.1017   **
> >
> >As you can see, it's not showing the second level of the factor  tridiff
> >(tridiff2) interacting with Decision Aids. I realise this is probably due
> >to redundancy or something of that sort, but we would like to see it
> >printed out. Is that at all possible?
> >
> >Thank you for your time and any insight you can provide,
> >Shannon
>



-- 
Shannon Duncan
Associate Director
Center for Decision Sciences
Columbia University
shannon at decisionsciences.columbia.edu

	[[alternative HTML version deleted]]