Software Project Duration and Effort: An Empirical Study

Software projects frequently finish late and over budget. Much of the research to date has characterized this problem in terms of inadequate project estimation or incomplete requirements determination. In this study, we concentrate instead on understanding the relationship between project duration and project effort. Over time, a dynamic environment contributes to the expansion of project requirements, thus increasing the scope and effort required to complete the project, irrespective of initial requirements and anticipated project size. Further, frequent delays and interruptions in a project contribute to greater effort each time work is resumed. We develop and empirically evaluate a two-stage model to relate project duration and effort. Our results indicate a significant and positive relationship between project duration and effort, controlling for anticipated project size and other project characteristics. Our model also provides an estimate for the rate of environmental change while projects are in progress. We demonstrate the practical implications of our model by showing how it can be used in conjunction with time boxing techniques and new development methodologies to better scope software projects.