[R-meta] correlation between pre and post test?

Hi everyone,

Thank you very much for the helpful suggestions.

Philippe:

By 'If all the studies present pre and post (and you don't have any 
study with change score) you can do a SMD only using the post 
measures', do you mean use post SD as the standardizer to calculate 
the SMD?

Michael:

1. If I use change scores as the effect size, can I use the pre and 
post means and SDs to calculate the effect size and the standard error?

2. By using a range of plausible pre-post correlations for a 
sensitivity analysis, do you mean providing a correlation coefficient 
for all of primary studies and save the results, then change the 
correlation coefficient to another value for all the primary studies, 
and run the analysis again, see if the two sets of results are 
significantly different? Is it possible to do the significant test?

Mike:

I do not have access to SAS or Stata, do you know any R implementation 
example code using Riley(2008) method?

Thank you very much guys.

Best regards,

YA


------------------?Original?------------------
*From:* "Philippe Tadger" <philippetadger at gmail.com>;
*Date:*?Wed, Aug 25, 2021 08:54 PM
*To:*?"Michael 
Dewey"<lists at dewey.myzen.co.uk>;"YA"<xinxi813 at 126.com>;"r-sig-meta-analysis"<r-sig-meta-analysis at r-project.org>;
*Subject:*?Re: [R-meta] correlation between pre and post test?

Dear YA

You can use correlation imputations from similar studies, or if this 
is not available you can use a mean difference estimation (not SMD) 
between the post and the change scores. If all the studies present pre 
and post (and you don't have any study with change score) you can do a 
SMD only using the post measures. All of this are common practices 
that you can find in Cochrane book, and basic MA books.


On 25/08/2021 14:45, Michael Dewey wrote:

If you are planning to analyse the change scores you will be OK with 
the mean change and its standard error. Otherwise try fitting with a 
range of plausible correlations and see how sensitive the results are 
to the assumed value.

Michael

On 25/08/2021 04:28, YA wrote:

Dear list,


I am trying to do meta analysis with random control trial research 
that has experiment and control group, and pre and post test. 
According to the meta analysis books, for these kind of research, I 
need the mean and SD for the experiment and control group at both 
pre and post test, I also need the correlation between pre and post 
test. The means and SDs are usually reported by the authors, but the 
correlations are usually not reported. How do I obtain the 
correlations between the pre and the post test?


Thank you very much.


Best regards,


YA
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-- 
Kind regards/Saludos cordiales
*Philippe Tadger*
ORCID <https://orcid.org/0000-0002-1453-4105>, Reseach Gate 
<https://www.researchgate.net/profile/Philippe-Tadger>
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