Although it may be difficult to require participation in Elluminate sessions, there seems to be a correlation between participation in synchronous activities and successful course completion. (North, 2005)
Clark, R. C. (2005) Harnessing the virtual classroom. Training & Development , 59(11), 41-45 . Available online at http://www.clarktraining.com/content/articles/HarnessingTheVC.pdf
Clark, R. C. & Mayer, R.E. (2007) E-learning and the science of instruction – 2 nd ed. San Francisco, CA: Pfeiffer.
North, M.A. (2005) Assessing the value of a synchronous seminar component in online database classes. Issues in Information Systems, VI(1), 156-162. Available online at www.iacis.org/iis/2005_iis/PDFs/North.pdf