The HESI predictability model (HPM), a proprietary mathematical model, is used to calculate all HESI scores. This calculation does not produce a percentage score, but reflects an application of the mathematical model to the raw scores of each student. It is the HESI score that is used to predict the likelihood of student success on the NCLEX examination.

The HPM considers several factors, including the difficulty level of each test item, and performs regression analyses for each score reported on every Evolve Reach - Powered by HESI exam. For example, a HESI score of 850 (considered the minimally-acceptable level) might be a percentage score of 65%, depending on the difficulty level of the test items answered correctly on a particular exam or in a particular test category.

Evolve Reach - Powered by HESI exams report a large number of different HESI scores. Each includes a total score and is followed by scores on each of the specialty areas tested. In addition, scores in several other categories are provided:

• Nursing process
• NCLEX Client Needs (National Council of State Boards of Nursing, 2001)
• National League for Nursing Accrediting Commission (NLNAC) Required Outcomes (National League for Nursing Accrediting Commission, 2003)
• American Association of Colleges of Nursing (AACN) Essentials of Baccalaureate Nursing, recognized by the Commission on Collegiate Nursing Education (CCNE) (American Association of Colleges of Nursing, 1998)

Every exam returned to Elsevier and HESI for development of an aggregate summary analysis undergoes an item analysis. As a measure of reliability, the KR-20 is calculated for each exam analyzed and the point biserial correlation coefficients are calculated for each item contained on an exam. These data are stored in the Evolve Reach system and used in the calculation of projected reliability for each exam administered.