The ability to gather immediate feedback is critical to the process of continuous improvement.
Instantaneous responses allow professors to make mid-class corrections in their lectures.
As class size increases, the professor's ability to check for understanding and learning of individual students decreases proportionately. Imagine trying to collect feedback from 240 physics students simultaneously. It can be done. In this particular physics class, the professor starts each day by lecturing for about 10 minutes. Then he asks a set of questions that he describes as a concept test.