The Use of Differential Item Functioning (DIF) Analysis to Distinguish Between Similar Job Roles

Two primary roles in the clinical laboratory are those of Medical Technologist (MT) and Medical Laboratory Technician (MLT). Job analyses, which form the foundation of test blueprints employed for credentialing practitioners, suggest a reasonable amount of overlap in the tasks performed by MTs and MLTs. However, credentialing assessments must clearly distinguish between the two roles and ensure that they address competencies appropriate to each practice designation. Differential item functioning (DIF) analysis techniques were applied to explore and differentiate the two laboratory practitioner job roles as an aspect of examination development. Results from the analysis suggest a high degree of similarity between these two groups in terms of scope of tasks performed. Subject matter expert interpretation suggests that the assessments are more appropriately differentiated by underlying level of task knowledge rather than scope of tasks. DIF may be applicable to other exploratory investigations that seek to differentiate job roles comprised of common competencies.