School of Statistics;
Shandong University of Finance and Economics;
Jinan 250014;
Shandong;
China;
College of Science;
China University of Petroleum;
Qingdao 266580;
Shandong;
China;
Zhongtai Securities Institute for Financial Studies;
Shandong University;
Jinan 250100;
Shandong;
China;
School of Mathematics and Statistics;
Shandong Normal University;
Jinan 250014;
Shandong;
China;