  An educational system, the tutor-web (http://tutor-web.net), has been
developed and used for educational research. The system is accessible and free
to use for anyone having access to the Web. It is based on open source software
and the teaching material is licensed under the Creative Commons
Attribution-ShareAlike License. The system has been used for computer-assisted
education in statistics and mathematics. It offers a unique way to structure
and link together teaching material and includes interactive quizzes with the
primary purpose of increasing learning rather than mere evaluation.
  The system was used in a course on basic statistics in 2011. Three types of
data were gathered during the course. A randomized crossover experiment was
conducted to assess the possible difference in learning (measured by repeated
exams) between students using the system and students doing regular homework.
The difference between the groups was not found to be significant. Responses to
quiz questions were collected and analysed with item response theory type
models. These analysis were used to improve the item banks. Finally, the
students answered an in-class survey regarding their experience using the
tutor-web. The responses of the students gave clear indications of student
preferences.
