[R] Classic fail-safe N

Viechtbauer Wolfgang (SP) wolfgang.viechtbauer at maastrichtuniversity.nl
Mon Jun 26 09:39:37 CEST 2017

I would suggest to post this to the (recently created) R-sig-meta-analysis mailing list. See:



>-----Original Message-----
>From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Naike Wang
>Sent: Monday, June 26, 2017 08:32
>To: R-help at r-project.org
>Subject: [R] Classic fail-safe N
>Hi all,
>I was conducting a meta-analysis of single proportions(i.e. without a
>control group) using the metafor package. When I performed a classic
>fail-safe N, I noticed that the result (the number of missing studies that
>would bring p-value to the alpha, to be exact)was different than that I
>in Comprehensive Meta-Analysis Version 2.0. I wonder why R and CMA got
>different results.
>*Below is the R code:*
>dat=read.table("Your working directory\\Example.csv",header=T,sep=",")
>transf.ies=escalc(xi=cases,ni=total,measure="PLO",data=dat) #I transform
>the data using the logit transformation first. In CMA, it also uses the
>logit transformation.
>transf.pes=rma(yi,vi,data=transf.ies,method="DL",weighted=TRUE) #Pooling
>individual effect sizes in the logit scale.
>ranktest(transf.pes) #Performing the fail-safe N.
>*Below are the results from R:*
>Fail-safe N Calculation Using the Rosenthal Approach
>Observed Significance Level: <.0001
>Target Significance Level:   0.05
>Fail-safe N: 8446
>*Below are the Classic fail-safe N results from CMA:*
>Z-value for observed studies 19.91594
>P-value for observed studies 0.00000
>Alpha 0.05000
>Tails 2.00000
>Z for alpha 1.95996
>Number of observed studies 58.00000
>Number of missing studies that would bring p-value to > alpha 5931.00000
>Notice that I got 8446 in R and 5931 in CMA.
>Can anyone shed some light on this discrepancy? Thank you!
>You can find my data set here:

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