Abstract
Different words, numeric values or semiotic registers, figures, graphs or tables, namely elements of item formulation, affect students’ probability of encountering an item correctly. An experimental study was carried out to compare different formulations and their effect for validating a comparative technique. Four anchored math achievement tests were administered to a sample of 1647 students attending grade 8 to explore students’ misconception about the relationship between perimeter and area. Results confirmed that item formulation channels students’ solving strategy and thus modifies the probability of a correct answer more than item content.