I am currently writing my thesis on professionalized political Twitter profiles, and I have created two indeces to measure professionalization, the dependent variable: an advanced user index consisting of 15 variables and one personalized index with 8 variables. My supervisor told me to combine these two variables into one when doing a regression analysis, but he said I have to do a mathematical "trick" because there are an unequal number of variables in the two indeces. I do not know how to do this. I am not allowed to get any more supervision from him now as I have reached the max nr of meetings. Does anyone know how to do this? I need help!