We have developed a WBT system named “CollabTest” that enables students to create quizzes collaboratively. Moreover the system has been using for many course works in the trial of our university. From the results of the questionnaires about CollabTest, we obtained such favorable answers as improvement of comprehension levels by creating quizzes, learning effect by mutually solving quizzes created by students, and improvement of learning motivation by peer assessment of quizzes. However, these results were not enough evidence to prove learning effect of CollabTest. In this paper, we formed hypotheses about learning effect expected by using CollabTest and tried to verify them through demonstration experiments. As the results of experiments, we could show that creating, reviewing and answering quizzes by using CollabTest improved test score and the test score is strongly correlated with utilization degree of CollabTest.
