Preference of epidemiological studies for establishing causality:-
RCT > Retrospective coho > Prospective coho > Case control > Cross sectional RCT > Prospective coho > Retrospective coho > Case control > Cross sectional RCT > Prospective coho >Retrospective coho > Cross sectional > Case control RCT > Retrospective coho > Prospective coho > Cross sectional > Case control