Primary claim in expository text

Some educators have suggested that sound-absorbing wall panels can make spoken lessons easier to understand in echoing classrooms. Researchers tested this idea in 22 comparable classrooms, installing acoustic panels in 11 rooms and leaving 11 rooms unchanged. After recorded lessons were played at the same volume, students in rooms with panels answered a median of 84 percent of comprehension questions correctly, compared with 70 percent in unchanged rooms. The experiment used brief recorded lessons rather than ordinary classes taught by different instructors. The findings indicate that, in the tested rooms, reducing echoes with acoustic panels improved comprehension of spoken material.