[R-meta] Impact of very high tau-square value.

Guido Schwarzer @c @end|ng |rom |mb|@un|-|re|burg@de
Wed Jun 26 11:28:20 CEST 2019

Dear Jide Ogbu,

It is not possible to give any specific advice on your dataset as you do 
not provide sufficient information. So, I will make some general comments.

A plethora of methods to estimate tau-squared is available (Veroniki et 
al., 2016) and they can give different estimates; see argument 'method' 
in metafor.

Furthermore, whether a tau-squared value of 32.8 is large depends on the 
outcome measure (and for some outcomes on the underlying metric). This 
value could be judged to be small if you are interested in a mean 
difference - depending on your metric. However, if your outcome measure 
is a standardized mean difference or a log odds ratio a tau-squared 
value of 32.8 would be very extreme.

Best wishes, Guido

Veroniki AA, Jackson D, Viechtbauer W, Bender R, Bowden J, Knapp G, et 
al. Methods to estimate the between-study variance and its uncertainty 
in meta-analysis. Research Synthesis Methods. 2016;7:55–79.

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