I DID MY M.Phil. in Discriptive analysis. NOW I like to Leads to Phd same topic but expand my M.phil. only change the analysing model as structural equation modelling.
SEM analysis may be applied to existing data sets, even those that may have been initially descriptive in intent. Witness the number of instances of people doing secondary analyses on various, large-scale survey study data sets.
In your situation, I think the bigger question is whether your Ph.D. examining committee would approve a given study as a suitable demonstration of your ability to conduct research in a competent manner. Standards can and do differ across committees, major professors/advisors, programs, and institutions. Check first!