The disadvantage of effect coding is that you refer to the
average of all the categories instead of a specific reference
category, and hence make your results specific to your study population.
With effect coding you can give a value for every category within a comprehensive table
as long as you remember to state in the legend of the table that the results
are not generalizable beyond you study population.
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> -----Original Message-----
> From: A UK-based worldwide e-mail broadcast system mailing
> list [mailto:[log in to unmask]] On Behalf Of Rik Van de Kerckhove
> Sent: 18. maj 2009 12:27
> To: [log in to unmask]
> Subject: Re: Effect coding vs Reference coding.
> Hi Gemma,
> the advantage of effect coding is you actual refer to the
> average of all the categories instead of a specific reference
> category. With effect coding you can give a value for every
> category within a comprehensive table, with reference coding
> you can't. The advantage of reference coding is obviously the
> calculation of odds ratios. In practice I always use effect
> coding for nice output tables (so all the categories can get
> a specific value) and reference coding for answering specific
> policy or research questions (with odds ratios).
> Hope this helps a bit.
> Dr. Rik Van de Kerckhove
> On 18/05/2009, Gemma Robson <[log in to unmask]> wrote:
> > Hi All,
> > I am trying to find a list of advantages/disadvantages for using
> > Effect coding vs using Reference coding within Logistic Regression
> > when using categorical predictor/explanatory variables.
> > Any advice would be greatly appreciated.
> > ________________________________________
> > Gemma Robson
> > Education Consultant ” SAS Customer Services
> > Tel: +44 (0)161 888 2032 ” Mobile: 07795 442 774 ”
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