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 <kende...@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]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://www.joshuawiley.com/ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
