Dear all,
  Today, i was thinking the following question.
We know the variables may be classified into continuous, ordinal, and
categorical variables. I was confused about how to handle with
the categorical variables in the multi-level models.
For fixed effects,  the categorical variables were always treated as dummy
variables, my questions are:
1. Could the random slope be specified for categorical variables that was
always changed into the form of  dummy variables?
2. If  the random slope could be specified for categorical variables, how to
explain it? It seems a little different from the continuous variables.
  I tried the GLIMMIX Procedure in SAS. It seems that SAS treats categorical
variables as  continuous variables. While in MLWin, it seems that random
slope could be specified for the dummy variables .
  Any ideas on it are greatly appreciated.

-- 
With Kind Regards,

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ZhiJie Zhang ,PhD
Dept.of Epidemiology, School of Public Health,Fudan University
Office:Room 443, Building 8
Office Tel./Fax.:+86-21-54237410
Address:No. 138 Yi Xue Yuan Road,Shanghai,China
Postcode:200032
Email:epistat@gmail.com <Email%3Aepistat@gmail.com>
Website: www.statABC.com
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