A stability assessment of solution adaptation techniques for analogy-based software effort estimation

Among numerous possible choices of effort estimation methods, analogy-based software effort estimation based on Case-based reasoning is one of the most adopted methods in both the industry and research communities. Solution adaptation is the final step of analogy-based estimation, employed to aggregate and adapt to solutions derived during the case-based reasoning process. Variants of solution adaptation techniques have been proposed in previous studies; however, the ranking of these techniques is not conclusive and shows conflicting results, since different studies rank these techniques in different ways. This paper aims to find a stable ranking of solution adaptation techniques for analogy-based estimation. Compared with the existing studies, we evaluate 8 commonly adopted solution techniques with more datasets (12), more feature selection techniques included (4), and more stable error measures (5) to a robust statistical test method based on the Brunner test. This comprehensive experimental procedure allows us to discover a stable ranking of the techniques applied, and to observe similar behaviors from techniques with similar adaptation mechanisms. In general, the linear adaptation techniques based on the functions of size and productivity (e.g., regression towards the mean technique) outperform the other techniques in a more robust experimental setting adopted in this study. Our empirical results show that project features with strong correlation to effort, such as software size or productivity, should be utilized in the solution adaptation step to achieve desirable performance. Designing a solution adaptation strategy in analogy-based software effort estimation requires careful consideration of those influential features to ensure its prediction is of relevant and accurate.