Thank you very much for your illustration, Wolfgang! It helped me a lot. And also thank you for the package-hint, Michael!
Now, I have re-checked the respective studies, and there still are a couple of studies left, only stating cohens d, and the respective t-value and p-value - sample and group sizes are not addressed (its data from an older meta-analysis). Is there a way to embed these studies in my sample? Wolfgangs illustration addresses only cases in which group sizes are stated, if I understand you correctly... Many thanks in advance, Verena On Sat, Apr 26, 2014 at 1:38 PM, Michael Dewey <i...@aghmed.fsnet.co.uk>wrote: > At 20:34 25/04/2014, Viechtbauer Wolfgang (STAT) wrote: > >> If you know the d-value and the corresponding group sizes for a study, >> then it's possible to add that study to the rest of the dataset. Also, if >> you only know the test statistic from an independent samples t-test (or >> only the p-value corresponding to that test), it's possible to back-compute >> what the standardized mean difference is. >> >> I added an illustration of this to the metafor package website: >> >> http://www.metafor-project.org/doku.php/tips:assembling_data_smd >> > > Verena might also like to look at the compute.es package available from > CRAN to see whether any of the conversions programmed there do the job. > > > > Best, >> Wolfgang >> >> -- >> Wolfgang Viechtbauer, Ph.D., Statistician >> Department of Psychiatry and Psychology >> School for Mental Health and Neuroscience >> Faculty of Health, Medicine, and Life Sciences >> Maastricht University, P.O. Box 616 (VIJV1) >> 6200 MD Maastricht, The Netherlands >> +31 (43) 388-4170 | http://www.wvbauer.com >> >> > -----Original Message----- >> > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org >> ] >> > On Behalf Of Michael Dewey >> > Sent: Friday, April 25, 2014 16:23 >> > To: Verena Weinbir >> > Cc: r-help@r-project.org >> > Subject: Re: [R] Metafor: How to integrate effectsizes? >> > >> > At 12:33 25/04/2014, you wrote: >> > >Thank you very much for your reply and the book recommendation, >> Michael. >> > > >> > >Yes, I mean Cohen's d - sorry for the typo :-) >> > > >> > >Just to make this sure for me: There is no >> > >possibility to integrate stated Cohens' ds in an >> > >R-Metaanalysis (or a MA at all), if there is no >> > >further information traceable regarding SE or the like? >> > >> > If there is really no other information like >> > sample sizes, significance level, value of some >> > significance test then you would have to impute a >> > value from somewhere. That would seem a last resort. >> > >> > I have cc'ed this back to the list, please keep >> > it on the list so others may benefit and contribute. >> > >> > >> > >best regards, >> > > >> > >Verena >> > > >> > > >> > >On Fri, Apr 25, 2014 at 1:21 PM, Michael Dewey >> > ><<mailto:i...@aghmed.fsnet.co.uk>i...@aghmed.fsnet.co.uk> wrote: >> > >At 13:15 24/04/2014, Verena Weinbir wrote: >> > >Hello! >> > > >> > >I am using the metafor package for my master's thesis as an R-newbie. >> > While >> > >calculating effectsizes from my dataset (mean values and >> > >standarddeviations) using "escalc" shouldn't be a problem (I hope ;-)), >> > I >> > >wonder how I could at this point integrate additional studies, which >> > only >> > >state conhens d (no information about mean value and sds available), to >> > >calculate an overall analysis. Ã I would be very grateful for your >> > support! >> > > >> > > >> > >You mean Cohen's d I think. >> > > >> > >You will need some more information to enable >> > >you to calculate its standard error. Have a look at Rosenthal's chapter >> > in >> > >@book{cooper94, >> > >Ã Ã author = {Cooper, H and Hedges, L V}, >> > >Ã Ã title = {A handbook of research synthesis}, >> > >Ã Ã year = {1994}, >> > >Ã Ã publisher = {Russell Sage}, >> > >Ã Ã address = {New York}, >> > >Ã Ã keywords = {meta-analysis} >> > >} >> > >(There is an updated edition) >> > >This gives you more information about converting >> > >effect sizes and extracting them from unpromising beginnings. >> > > >> > >It often requires some ingenuity to get the >> > >information you need so have a go and then get >> > >back here with more details if you run into problems >> > > >> > > >> > >Best regards, >> > > >> > >Verena >> > > Michael Dewey > i...@aghmed.fsnet.co.uk > http://www.aghmed.fsnet.co.uk/home.html > > [[alternative HTML version deleted]]
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