The BACB uses the modified Angoff method for establishing the passing score for each “base” exam form. Subsequent exam forms are statistically equated to the base exam form to ensure that any differences in difficulty level are taken into account. As a result of the equating process, the pass rates generally remain quite stable throughout the life span of each “base” exam form. New “base” exam forms are ertreated approximately every five years or whenever there is a significant change to the exam content, such as the introduction of a new Task List. Periodic replacement of the base exam is required to ensure that the items on the base exam do not become over-exposed to candidates. Items that become over-exposed may no longer accurately measure the candidates’ knowledge of the required content.
The modified Angoff method is a criterion referenced method that relies on the judgment of a panel of subject matter experts, who hold BACB credentials. The panel members are carefully selected to be a representative sample of the overall population of credential-holders based on a variety of factors, such as experience, type of practice, and geographic region. The experts participate in a training exercise which orients them to the passing-score process prior to estimating the percentage of minimally competent candidates who will know the answer to each item. The ratings for the entire panel of experts are then averaged together to arrive at a recommended passing score. The recommended passing score is then reviewed and approved by the Board of Directors.