Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.|Department of Statistics and Operations Research, Chapel Hill, NC, USA.