Advances in information and communication technologies have given impetus to e-learning as choice educational environment for million of learners. E-learning involves the use of Internet technology to provide education where the instructor and students operate without geographical boundaries. Despite positive strides made in e-learning, the drop out rate of students remains high. Most educators argue that interactivity of learners is central to the success of e-learning initiatives. Accordingly, we present an interactivity model to dynamically measure interactivity in the context of elearning. The model leverages a common term vocabulary and Chebyshev's inequalities to objectively measure the contributions of participants in a group work. We evaluate the performance of our model using extensive simulation studies.
