The quality of automatic translations these days never ceases to astonish me.
I would like to ask, when designing DCE with SAS software, how to add constraints so that there are no two levels that cannot be combined, leaving only reasonable combinations? For example, there are two levels of consultation: online consultation and offline consultation, and nucleic acid testing has two levels: yes and no. Online consultation can only be combined with the absence of nucleic acid testing. What syntax can be used in SAS to implement this constraint?
... View more