Students in the first statistics course generally have trouble reasoning about statistics and the concept of probability. The reform movement tin teaching statistics suggests a variety of good practices. In an attempt to increase student learning, we have researched the use of active learning, cooperative groups, and authentic assessment. In this study we have added web-based instructional materials and on-line small group discussion activities. This classroom-based research looks at an aspect of learning we have not studied previously, reasoning about probability. Due to the large size of this section of sophomore level statistics (N=126), student interaction in thinking g through activities was captured electronically through the use of WebCT on-line group discussion. The on-line discussion format had both strengths and weaknesses, which will be discusses. The WebCT content of the group discussions on-line was captured and analyzed to determine how students reasoned through the activity. The purpose of this study was to explore students' reasoning in completing group-based activities on probability.