1. Quality Initiatives Division, Health Net, Woodland Hills, California
2. Department of Biostatistics, University of California Los Angeles, Los Angeles, California
3. Quality Initiatives Division, Health Net, Woodland Hills, California, Department of Biostatistics, University of California Los Angeles, Los Angeles, California
4. Quality Initiatives Division, Health Net, Woodland Hills, California, Department of Community Medicine, Mount Sinai School of Medicine, New York, New York