I have a response, "Satisfaction" that goes on a scale from 0-10 (where 0=dissatisfied and 10= very satisfied), and I have a predictor variable that also uses the same scale. I recoded the response so that 0-5 is "not satisfied" and 6-10 is "satisfied". I did the same for the predictor variable. I used SPSS to get the frequencies for each (there are 4 different combinations). My question is, can I use a two proportion z-test to test whether there is a significant difference in the predictor at the two different levels of my response?