I am performing a polychoric correlation to use in Principal Component Analysis.  The data are mostly Likert scale (4 levels), with a sample size of 68.  For some questions in the survey, there were only a few responses (1-4 out of 68) for certain numbers.  I know for Chi-Square tests (ordinal or otherwise), you have to combine some cells together first when that happens (if the expected value will be less than 5).  Do I also need to combine cells first for polychoric correlation? ... View more