Virtual Experiments and their Role in Teaching Design and Analysis of Experiments

The ability to design experiments in an appropriate and efficient way is an important skill, but students typically have little opportunity to get experience. Most textbooks introduce standard general-purpose designs, and then proceed with the analysis of data already collected. Some recent textbooks (e.g. Cobb 2002, Dean and Voss 1998) stress the importance of including projects in which the students actually have to prepare, perform and analyze a real experiment. Such projects provide an invaluable experience, but are very time and resource consuming, for the student as well as for the teacher. In this paper we explore an additional tool for gaining design experience: computer based virtual experiments. What we call “virtual experiments” are software environments, which mimic a real situation of interest, and invite the user to collect data to answer a research question. The data are generated by an underlying realistic stochastic model, invisible to the user. Once the data are collected, they can be transferred to a standard statistical package. The user can train his/her design skills by relating the quality of the statistical results obtained to the data collection strategy used. A number of such environments have been implemented. The collection is called VIRTEX (VIRTual EXperiments), and is a companion to the VESTAC collection, previously developed for other statistical purposes (Darius et al. 2000). The environments are all realized in the form of JAVA applets, and are freely available on the web at http://www.kuleuven.ac.be/ucs/virtex/ . They can be run on any computer with a web browser that supports JAVA (the vaccine applet needs the SUN virtual machine). Due to the safety requirements of applets, they cannot read or write data from or to the user’s hard disk. Yet data can be exchanged with other programs through cut and paste.