-----Original Message-----
From: David Fisher [mailto:djfisher81 at gmail.com]
Sent: Monday, 15 June, 2020 18:04
To: Viechtbauer, Wolfgang (SP)
Cc: Gerta Ruecker; r-sig-meta-analysis at r-project.org
Subject: Re: [R-meta] Problems using rma.mh
Hi Wolfgang,
Aha! It didn't occur to me that the error might be referring to the
output, rather than to the input. That makes total sense...and
thankyou for the suggestion to obtain the results directly from the
object!
I have had a play with subsets of studies and with the add(), to() and
drop00 options, and it seems that the following is true:
a) If the M-H pooling is done using corrected counts [ via e.g.
add=c(0, 0.5) to=c("only0", "only0") ] then the Breslow-Day (+/-
Tarone) statistic is also calculated using corrected counts, and hence
has a defined value;
b) If effect sizes for the individual studies are *not* calculated
using corrected counts [ again, via add=c(0, 0.5) to=c("only0",
"only0") ] then the Q statistic is zero/undefined.
Finally, regarding your observation that the Cochran-Mantel-Haenszel
test can still be conducted, even when all studies have zero events in
the same arm: this is presumably because the CMH test is very similar
to a Peto chi-squared test, which can be fitted in this scenario, e.g.
res.peto <- rma.peto(ai=ai, n1i=n1i, ci=ci, n2i=n2i,
data=dat[which(dat$ai==0),])
Many thanks for your work developing "metafor", and for your time
answering my questions.
Best wishes,
David.
On Fri, Jun 12, 2020 at 11:58 AM Viechtbauer, Wolfgang (SP)
<wolfgang.viechtbauer at maastrichtuniversity.nl> wrote:
Hi David, Hi Gerta,
Thanks for the note, David. This was an oversight in the printing
function. When there are no events at all in one of the arms across all
studies, then certain statistics cannot be computed, which are then NA. This
leads to problems when trying to format these values with sprintf(). I'll
fix this asap.
But rma.mh() itself works, so this is fine:
dat <- dat.nielweise2007
res <- rma.mh(measure="OR", ai=ai, n1i=n1i, ci=ci, n2i=n2i,
data=dat[which(dat$ai==0),])
If you are interested in the Breslow-Day and Tarone statistics, you can
still get them from the object with:
res$BD
res$TA
and the corresponding p-values with:
res$BDp
res$TAp
But in this case, you will find that both statistics are actually NA. In
other words, these tests cannot be conducted when there are no events in one
of the two arms. Or one would have to use continuity corrections, but the
point of the MH method and related statistics (such as BD and TA) is that
they do not require such corrections and in fact were never meant to be
combined with such corrections.
Interestingly, the Cochran-Mantel-Haenszel test can still be conducted:
res$CO
res$COp
Best,
Wolfgang