  A learning environment, 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 the University of
Iceland, spring 2013. A randomized trial was conducted to investigate the
difference in learning between students doing regular homework and students
using the system. The difference between the groups was not found to be
significant.
