[R-meta] egger's test for funnel plot symmetry of a `robu()` model

[Reza Norouzian]

Dear All,

I was wondering if my solution below correctly performs egger's test for a
`robu()` model from `robumeta` package in R? Specifically, Is my *p.value*
credible?

The idea is that after fitting a meta-analytic model (`*m1` below*), we
regress some measure of precision (e.g., SE of effect sizes; `*SD` below*),
on effect sizes (`*y` below*) themselves. If the slope for the regression
line is significant then that could suggest publication bias.

Thanks, Reza

d <- read.csv("https://raw.githubusercontent.com/izeh/m/master/e.csv",
h = T) # DATA

m1 <- robu(y~1, data = d, study = id, var = SD^2, small = FALSE)

X <- cbind(1, d$SD) ## SE as the predictor
## egger test:
egger <- robu(y ~ X - 1, data = d, var = SD^2, study = id, small = FALSE)
# p-value of X2 which suggests publication bias if significant:
egger$reg_table$prob[2]# > [1] 0.636

-- 
*Reza Norouzian*
Postdoctoral Research Associate | Lecturer
Second Language Acquisition & Research Methods, Ph.D.
College of Education & Human Development
Dep. of Teaching, Learning & Culture | Texas A&M University
College Station, TX 77843
Webpage: *https://directory.education.tamu.edu/view.epl?nid=rnorouzian
<https://directory.education.tamu.edu/view.epl?nid=rnorouzian>*
Email: rnorouzian using tamu.edu
Phone: (979)-422-7052
*Future L2 researchers will be challenged not only on the basis of their
substantive questions, but also on how they manage to answer those
questions in a methodical manner.*

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