The analysis of statistical data is a critical element in road safety studies. For example, specific projects or programs may be implemented with the analyst asked to answer the question, "What has been the effect of this project (program) on accident frequency and/or severity?" Are there any interdependencies or contribut ing effects due to the age, sex or driving experience of involved motorists? What is the contribution, if any, of roadway design, time of day, traffic density, etc.?" To answer, or to provide insight into, these types of questions, contingency tables are often used to...