[R] Metafor: How to integrate effectsizes?

[Michael Dewey]

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-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> > On Behalf Of Michael Dewey
> > Sent: Friday, April 25, 2014 16:23
> > To: Verena Weinbir
> > Cc: r-help at 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:info at aghmed.fsnet.co.uk>info at 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. Â 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,
> > >Â  Â author = {Cooper, H and Hedges, L V},
> > >Â  Â title = {A handbook of research synthesis},
> > >Â  Â year = {1994},
> > >Â  Â publisher = {Russell Sage},
> > >Â  Â address = {New York},
> > >Â  Â 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
info at aghmed.fsnet.co.uk
http://www.aghmed.fsnet.co.uk/home.html