Department of Statistics, North Dakota State University, Fargo, ND 58102, USA and Department of Statistics, Iowa State University, Ames, IA 50011, USA.|Department of Statistics, North Dakota State University, Fargo, ND 58102, USA and Department of Statistics, Iowa State University, Ames, IA 50011, USA.|Department of Statistics, North Dakota State University, Fargo, ND 58102, USA and Department of Statistics, Iowa State University, Ames, IA 50011, USA.