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[R-meta] Covariance-variance matrix when studies share multiple treatment x control comparison

Ju Lee 
Dear James, Wolfgang,

Thank you very much for this information.
I have one question extending from this is: While I run my main mixed modes always using var-covar. matrix (to account for shared study groups within each study),
it is acceptable that my egger-like regression does not incorporate this structure, but rather just use sqrt(1 / n1 + 1 / n2)  as precision (instead of sqrt(diag(v.c.matrix)) like Wolfgang suggested as one possibility) and use p-value for precision term (precision.2 which is p=0.2382) to determine the asymmetry?

prec.<-function(CN,TN){
  pr<-sqrt((1 / CN) + (1/TN))
  return(pr)
}
precision.2<-prec.(MHF$n.t, MHF$n.c)
Multivariate Meta-Analysis Model (k = 285; method: REML)
Variance Components:
  estim    sqrt  nlvls  fixed  factor
sigma^2.1  0.4255  0.6523     73     no   Study
sigma^2.2  0.3130  0.5595    285     no      Id
Test for Residual Heterogeneity:
  QE(df = 283) = 1041.1007, p-val < .0001
Test of Moderators (coefficient(s) 2):
  QM(df = 1) = 1.3909, p-val = 0.2382

Model Results:
  estimate      se     zval    pval    ci.lb   ci.ub
intrcpt        0.0529  0.1617   0.3274  0.7433  -0.2640  0.3699
precision.2   -0.0668  0.0567  -1.1794  0.2382  -0.1779  0.0442
---
  Signif. codes:  0 ?***? 0.001 ?**? 0.01 ?*? 0.05 ?.? 0.1 ? ? 1


Thank you very much, both of you.
Best,
JU

p.s. Wolfgang, I think I figured out what went wrong with how I specified my random effects in my previous e-mail. Specifying it as random=list(~factor(x)|Study, ~factor(x)|Id) instead of random= ~factor(x)|Study/Id generates results that makes sense to me now. Please let me know if this is correct way I should be coding.
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Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 18 Wolfgang Viechtbauer Covariance-variance matrix when studies share multiple treatment x control comparison Sep 18 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 18 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 18 Wolfgang Viechtbauer Covariance-variance matrix when studies share multiple treatment x control comparison Sep 24 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 25 Wolfgang Viechtbauer Covariance-variance matrix when studies share multiple treatment x control comparison Sep 26 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 26 Wolfgang Viechtbauer Covariance-variance matrix when studies share multiple treatment x control comparison Sep 26 James Pustejovsky Covariance-variance matrix when studies share multiple treatment x control comparison Sep 26 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 26 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 26 James Pustejovsky Covariance-variance matrix when studies share multiple treatment x control comparison Sep 26 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 27 Wolfgang Viechtbauer Covariance-variance matrix when studies share multiple treatment x control comparison Sep 27 Ju Lee Covariance-variance matrix when studies share multiple treatment x control comparison Sep 27