What's the most probable sorority/fraternity?

Using the list of the fraternities and sororities on North-American Interfraternity Conference and the National Panhellenic Conference wikipedia pages I did a quick and dirt frequency analysis (more commonly used for cryptography/code breaking).

Apparently for a sorority AΔΣ is the combination of the most popular letters, while ΔΣΦ takes it for the frats.