I have a set of data about some students and I want to check if their success in exams is determined by their level of technological knowledge, or their school. So, I have a table with those values (left) and I converted into numeric values (right):
I did this so I can apply correlation and analyze if there are a strong relation between variables, like this way:
This let me see that when the note is good, the users are generally of basic level. And that students of APS use to have good notes. But there is no sense with the middle matchings (-0,57).
The thing is: is it ok to perform such transformations to the original data? or should I use another method for knowing the level of relation between a qualitative data and quantitative one? Thank you!