Welcome to Probability Theory Online at the School of Mathematics Cardiff. The aim of these pages is to aid the understanding of Probability Theory by investigating various examples, exercises and illustrations. Use the Navigation bar on the left to find your way around the site. It is separated into three different sections: Probability Theory, Discrete Distributions and Continuous Distributions. Each of these sections has its own index page and when you are within a particular section you can also navigate to the "next" or "previous" page in that section. It should be noted that these pages contain numerous interactive applications, as a result a Java/JavaScript enabled browser is required. For full details on the methods used see the Notes on Navigation page. To improve the download time of some of the applets used a free download is available from the Design Science Website however, every effort is being made to make these pages available and accessible to all. I hope you find the site helpful and interesting. Why not take a chance and take a look?