I have a problem, right now i'm on my undergraduate thesis, my thesis is about the relation between internal audit (X) and internal control report (Y). For X, i need to go on questionnaires, and for Y, i just need to compare the report with the guidelines

Since my questionnaires is based on likert scale, so the data will be ordinal data, anda for Y, the data will be on interval scale. Since the scale is different, i can't use them to test the spearman correlation between them

My question is, are there any method to change my ordinal data into interval? I've heard about methods of successive interval (MSI), but i can't find any guides about that on google. Could you help me explainning what do i have to do in order to change the scale from ordinal to be interval?

Thank you very much for your help..