type
 TSampleType = (stX, stY, stZ);
 TSampleTipes = set of TSampleType;

private
 FSampleType : TSampleTipes;

function GetInfoAboutSampleType() : String;
begin
 case Integer(FSampleType) of
      0 : Result := stX;
      1 : Result := stY;
      2 : Result := stZ;
   0, 1 : Result := stX + stY;
   0, 2 : Result := stX + stZ;
   1, 2 : Result := stY + stZ;
     else Result := stX + stY + stZ;
 end;
end;