Does ANYONE understand the symmetry model for categorical data analysis by Agresti? I have a Likert scale that places students into 4 categories. I am doing a pretest-posttest design, so I will give them the scale at T1, then again later at T2. I will construct a 4x4 table. How do I find out if significant change occurred between categories from T1 to T2? I can't use chi square, must use symmetry model and SAS software (Unless someone knows how to do matched pair analysis in SPSS...). Any suggestions?