Department of Statistical Science, Southern Methodist University, Dallas, Texas, USA. jcao@smu.edu|Department of Statistical Science, Southern Methodist University, Dallas, Texas, USA. jcao@smu.edu|Department of Statistical Science, Southern Methodist University, Dallas, Texas, USA. jcao@smu.edu|Department of Statistical Science, Southern Methodist University, Dallas, Texas, USA. jcao@smu.edu|Department of Statistical Science, Southern Methodist University, Dallas, Texas, USA. jcao@smu.edu