Omit observation for proc ttest

[toneill]

Basic question for a new user:

I have a class variable (Y) that has >2 levels (yes/no/don't know/refused). I would like to perform a 2-sample t-test to compare population means on a survey at baseline (Z = 1). However, I know that my class variable will return an error of too many levels. How do I exclude "don't know" and "refused" observations (thus, only leaving those participants who responded "yes" or "no" responses)?

title X ;

proc ttest data = X ;

     class Y ;

     var A ;

          where Z = 1 ;

run ;

Thank you.

[Haikuo]

Something like this? Pay attention to the case for 'yes' , 'no'

title X ;

proc ttest data = X (where=(Y in ('yes', 'no')) ;

  class Y ;

  var A ;

  where Z = 1 ;

run ;

[toneill]

Thank you Hai.kuo

Just one minor correction on the parentheses:

title X ;

proc ttest data = X (where=(Y in ('yes','no'))) ;

     class Y ;

     var A ;

          where Z = 1 ;

run ;

Works perfectly! Thanks for helping me learn another SAS trick!