International Journal on Artificial Intelligence Tools, Vol. 11, No. 3 (2002) 369–387 ❢ c World Scientific Publishing Company B-COURSE: A WEB-BASED TOOL FOR BAYESIAN AND CAUSAL DATA ANALYSIS PETRI MYLLYM ¨ AKI, TOMI SILANDER, HENRY TIRRI, PEKKA URONEN Complex Systems Computation Group (CoSCo) Helsinki Institute for Information Technology P.O.Box 9800, FIN-02015 HUT, Finland http://cosco.hiit.FI/ Received 8 December 2001 Accepted 18 March 2002 B-Course is a free web-based online data analysis tool, which allows the users to analyze their data for multivariate probabilistic dependencies. These dependencies are repre- sented as Bayesian network models. In addition to this, B-Course also offers facilities for inferring certain type of causal dependencies from the data. The software uses a novel “tutorial style” user-friendly interface which intertwines the steps in the data anal- ysis with support material that gives an informal introduction to the Bayesian approach adopted. Although the analysis methods, modeling assumptions and restrictions are to- tally transparent to the user, this transparency is not achieved at the expense of analysis power: with the restrictions stated in the support material, B-Course is a powerful anal- ysis tool exploiting several theoretically elaborate results developed recently in the fields of Bayesian and causal modeling. B-Course can be used with most web-browsers (even Lynx), and the facilities include features such as automatic missing data handling and discretization, a flexible graphical interface for probabilistic inference on the constructed Bayesian network models (for Java enabled browsers), automatic pretty-printed layout for the networks, exportation of the models, and analysis of the importance of the derived dependencies. In this paper we discuss both the theoretical design principles underlying the B-Course tool, and the pragmatic methods adopted in the implementation of the software. Keywords : Bayesian networks, causal networks, model selection, probabilistic inference, interactive tutorials, ASP 1. Introduction B-course is a free * online data (dependency) analysis tool motivated by the problems in the current practice in statistical data analysis. In many cases, when practitioners in various fields apply analysis tools, the underlying assumptions and restrictions are not clear to the user, and the complicated nature of the software encourages the * The B-Course service (http://b-course.hiit.fi or http://b-course.cs.helsinki.fi) can be freely used for educational and research purposes only.