[R-meta] Moderator level getting removed from model
Viechtbauer Wolfgang (SP)
wolfgang.viechtbauer at maastrichtuniversity.nl
Mon Feb 12 18:56:06 CET 2018
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
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