Invalid reference value for RUCA_3CAT.

[lsak]

This is my code to get OR and CIs. 

PROC LOGISTIC DATA=thesis;

CLASS RUCA_3CAT (ref = "Urban") / PARAM=REF;
MODEL mdro_res (EVENT = "negative") = RUCA_3CAT / ALPHA=0.03125;
RUN;

I am getting "Invalid reference value for RUCA_3CAT"

the categories for this are: urban,rural, suburban and for mdro_res: positive and negative

Can someone help me figure out what's wrong with my code? 

thanks 

[StatDave]

The value you specify in the REF= option must be the exact value (formatted value if the variable is formatted) including any spaces and with identical upper/lower case.

[ballardw]

Just to be pedantic:  "Urban" is not equal to "urban".