I have an interval scale survey data. I have defined the socioeconomic status of the survey site with 5 parameters and wish to create a composite index. I do not have any prior weights for these parameters. Can I use PCA to create an index? My data is satisfying KMO and Bartlett Sphericity test, but for the results to be robust is it important for the data to pass normality and "no non-linearity" tests as well? Some of my parameters are normal while some are not. Please guide.