Using poll sheets and computer vision as an inexpensive alternative to clickers

Classroom Response Systems, colloquially known as Clickers after the predominant hand-held input device, are widely used because they allow students to respond in class to questions posed by the lecturer. This improves active learning and interaction in large classes—students are more involved, and lecturers can assess understanding and even take remedial action. Unfortunately, Clicker systems are relatively expensive, particularly in a developing-world con- text. They typically cost $200–700 for a base station and $30–50 per Clicker.

In this paper we present an inexpensive alternative to Clickers. Poll sheets with coloured blocks printed on a white background are held up by the students and a camera- phone is used in panoramic mode to photograph the class. This image is then processed using computer vision to count and classify the students’ responses.

While the 85% recognition rate we achieve is certainly not as accurate as Clickers, this approach nevertheless has many of the same benefits for active learning at a fraction of the cost: $0.20 per poll sheet, assuming a laptop and camera-phone are already available.