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Message-ID: <CAHP6aVFqSuObb8Rs3soqkRQOafCdiuTLcm4C8PD0TP3dgp2T2Q@mail.gmail.com>
Date: 2020-06-08T19:59:28Z
From: Divya Ravichandar
Subject: [R-meta] How does rma handle effect size of zero

Hi all

I would like to get some understanding around how rma handles effect sizes
of 0. A test example is outlined below

library(metafor)
library(magrittr)

case1 <- data.frame(Study= c("a","b","c","d"),ES=rep(.1,4),SE=rep(1e-5,4))
%>% rma(ES, SE^2, data=.) #non zero case
meta_case1 <- rma(ES, SE^2,  data=case1)
case2 <- data.frame(Study= c("a","b","c","d"),ES=rep(0,4),SE=rep(1e-5,4))
%>% rma(ES, SE^2, data=.) #zero case

While case 1 results in a significant p value  (<.0001), case 2 results in
a non-significant p value (1). Does a zero effect size violate any
assumptions and if not I wonder why a consistent estimate of 0 across
datasets results in a non-significant result?

Thanks

-- 
*Divya Ravichandar*
Scientist
Second Genome

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