[R] Meta-analysis question

[Joshua Wiley]

Dear Jan,

It depends what you are looking to do.  For the studies that have
given you means and standard deviations, if you want a d effect size,
you should already be set (Mean1 - Mean2)/control standard deviation
or the pooled standard deviation if you prefer.  For the studies where
you just have p-values, assuming you also have the sample size:

qt(p = .05/2, df = 42)

will give you the t for a two tailed p-value of .05 on 42 degrees of
freedom, and t is basically just d * (sqrt(df)/2), so it is not
difficult to get a d effect size once you have the t value.

Of course all that makes quite a few assumptions about what data you
have and what you are trying to do.  For tools to help you in R, take
look at the rmeta package

http://crantastic.org/packages/rmeta

and I also recommend looking around crantastic for other packages that
might work for you.  There are handy tags like "similar packages" that
are a nice way to browse around, and when you're done with your
meta-analysis, check back there to add ratings/a review of the package
you used.

Cheers,

Josh

On Fri, Oct 8, 2010 at 8:14 AM, kende jan <kendejan at yahoo.fr> wrote:
> Dear all,
>
> I am trying to do meta-analysis of continuous outcome data. Twelve studies are
> selected but for six of them, i have only p-values and the six other means and
> standard deviation for the two groups (Experimental and Control). How can I do
> with R to take into account p-values and/or means and standard deviation to
> perform my meta-analysis.
>
> Thanks for your help
> Jan
>
>
>
>        [[alternative HTML version deleted]]
>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/