When we began developing the HALF Diagnostic Assessment in 2011, we created 60 multiple-choice assessment items. These items tested 15 different fractions skills. The design of these items was informed by a number of popular, research-based mathematics curricula, including RNP: Initial Fractions Ideas by the Rational Number Project, the Investigations curriculum by TERC, Everyday Mathematics by the University of Chicago School Mathematics Project, and Do the Math by Marilyn Burns/Scholastic.

Over the next three years, we conducted item development, testing, and analysis. The current item bank for the HALF Diagnostic Assessment includes 276 multiple-choice assessment items. A total of 1,734 students participated in one or more rounds of testing these items. During each round of item development and testing, we aimed to improve the existing items in the item bank as well expand the number of subdomains of fractions content covered by the assessment items.