Dr. Eric Chamot, associate professor in the department of epidemiology at the University of Alabama at Birmingham School of Public Health, along with colleague Dr. Gary R. Cutter, professor in the department of biostatistics, recently sought to present in accessible terms an application of bifactor confirmatory factor analysis to study the clinical disability outcomes in multiple sclerosis (MS). MS can affect virtually every neurological function, which complicates the conceptualization and assessment of disability. However, progress in diagnosis and outcome measurement has been recently achieved by capitalizing on the concept of bifactor model.