With only minimal changes to the course structure, classroom clickers were introduced in introductory chemistry to allow students to regularly compare their perceived abilities with their actual abilities, a measurement also known as calibration. Students used the clickers to provide knowledge judgments, an indication of their confidence in correctly answering questions, prior to actually answering the same assessment item. The clickers allowed responses from this exercise to be viewed by the entire class and permitted additional instruction when the perceived knowledge of the class did not match the actual performance. Overall, introducing this practice resulted in gains in student calibration accuracy from the beginning to the end of the semester. The improvements, however, were not equally distributed across all student groups.