Can somebody confirm whether the variables used in a Principal Components Analysis, such as on SPSS, ALL need to be interval level? I have 2 variables that are ordinal level, and don't know whether I can include them or not. Thanks a lot, L
As far as I know, a Principal Components Analysis in SPSS was purposively designed for analysing ordinal and nominal data. It uses several methods of optimal scaling and assigns quantitative values to qualitative scales.