I have three variables I'd like to analyze. Two of them are step values - one set ranges from 1-6 and the other ranges from 1-5. The third variable is not a step value but can have a relatively wide range of possible values. I'm trying to determine if my third variable is related/correlated to either of the two step values.

The step values represent differing pay grades and rankings while the non-step variable represents pay. How can I test if pay is related to pay grade and/or rankings? And is there a way to graph all three variables in one chart?