Are Size Measures Better Than Expert Judgment? An Industrial Case Study on Requirements Volatility

Expert judgment is a common estimation approach in industry. However, there is very little research on the accuracy of expert judgment outside the area of effort estimation. In this paper, we present an industrial case study investigating subjective and objective measures of requirementss volatility. Data was collected in retrospect for all use cases of a medium-size software project. In addition, we determined subjective volatility by interviewing developers and managers of the project. Our data analysis show that structural measures perform better than expert judgment in estimating the total number of changes to use case based requirements. These results confirm results from a previous case study by the authors and suggest that project managers should not rely on expert judgment alone for decision making.