[R-meta] overall efect size from subgroup analysis

[Viechtbauer, Wolfgang (SP)]

Dear Diego,

If these are 95% CIs computed based on a normal distribution, then we can back-calculate the standard errors with:

yi <- c(-48, -30, -15)
ci.lb <- c(-73, -38, -24)
ci.ub <- c(-12, -21, -6)
sei <- (ci.ub - ci.lb) / (2*1.96)

We can check if this yields the same bounds with:

round(yi - 1.96 * sei)
round(yi + 1.96 * sei)

This doesn't seem to work out for the first group, but for the second and third (the upper bound of -22 for the second group instead of -21 could just be a rounding error). Either there is a typo for the first group or the CI was obtained in a different way (as you mentioned bootstrapping in your first post). Are you sure it says -12 for the upper bound of the first group and not -22? Because then it would be fairly close again.

Ignoring this isse, you now have the estimates and corresponding SEs, so you can now pool them with:

library(metafor)
rma(yi, sei=sei, method="FE")

Best,
Wolfgang

>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On
>Behalf Of Diego Grados Bedoya
>Sent: Wednesday, 28 April, 2021 9:10
>To: Michael Dewey
>Cc: R meta
>Subject: Re: [R-meta] overall efect size from subgroup analysis
>
>Dear Michael,
>
>Sorry, I did not notice that the email was mangled.
>
>Thank for the link but I do not have access to the original data of the
>subgroups. I just have the effect sizes, CIs and number of comparisons
>(observations).
>
>subgroup CI_lower_limit effect_size CI_upper_limit number_comparisons
>group_1 -73 -48 -12 5
>group_2 -38 -30 -21 43
>group_3 -24 -15 -6 73
>
>Greetings,
>
>Diego
>
>On Tue, 27 Apr 2021 at 16:08, Michael Dewey <lists using dewey.myzen.co.uk> wrote:
>
>> Dear Diego
>>
>> I think you may find
>> https://metafor-project.org/doku.php/tips:comp_two_independent_estimates
>> helpful.
>>
>> Your data is close to unreadable as you posted in HTML and that becomes
>> mangled. If you need to re-post you have to find a way to send plain
>> text. I do not use Gmail but I am sure it is possible.
>>
>> Michael