[Rd] Bug in calculation of overdispersion for quasibinomial grouped

Ulrike Grömping groemping at bht-berlin.de
Mon Apr 26 22:36:13 CEST 2010


A quick addition:

SAS PROC LOGISTIC with option SCALE=PEARSON only calculates what R 
calculates in the grouped version; this is forced by refusing to 
calculate a FI estimate for ungrouped data, unless an AGGREGATE option 
is specified.

Apparently, SAS has decided for one model (not the one I am most 
familiar with), while the R version makes the model decision depend on 
the format of the data. As the family in glm is called quasibinomial, I 
would have expected it to conduct the adhoc adjustment.

Best, Ulrike

-- 
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* Ulrike Groemping                            *
* BHT Berlin - University of Applied Sciences *
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