Here is another plugin that lets you add exams to your website. The Exam Matrix WordPress Plugin allows you to creates timed tests for your site. Simply create your sets, subsets, add questions, and you are ready to go. Webmasters have the option to randomize questions and enable negative marking.
The neat part is you can import questions from a CSV file or export them for future use. For each question, you get to define time, marks, and other settings. You can also set the name and subset name for each question.