An Analysis of the Statistical Performance of the Certified in Public Health Examinations

Passing the Certified in Public Health (CPH) Examination is the first step in meeting the voluntary standard for public health professionals - the CPH credential. The Examination assesses an individual's mastery of the knowledge and skills relevant to contemporary public health as defined by the ASPH MPH competencies. Based on ~2,000 examinees since August 2008, there is robust statistical data showing that the CPH Examination meets rigorous psychometric performance benchmarks for an examination of its size and purpose. The KR20 reliability estimate has been consistently higher than 0.90. Mean item discrimination has ranged from 0.21 - 0.34 range, indicating that the test items do a good job distinguishing between high- and low-scoring examinees.

Exam items are developed by volunteers selected from schools and programs of public health and the NBPHE's practice partners to represent a diverse range of academic background, expertise, practice experience, ethnicity, gender, and geographic locations. Selection is competitive, based on experience and expertise in 12 competency areas, including biostatistics. Based on training and quality assurance procedures, a final examination form is readied with 200 multiple-choice questions. Biostatistics tends to be one of the more challenging domains for examinees. Leadership of the NBPHE sets the cut score. Equating allows comparison of performance across administrations.

Creating the body of unique, validated test questions was a first for public health, and the pool of professionals who have perfected item writing adds value to the field. The result is a rigorous exam to assess higher-order thinking across the public health sciences.