Optimized fuzzy clustering-based k-nearest neighbors imputation for mixed missing data in software development effort estimation

ContextSoftware development effort estimation (SDEE) is one of the most challenging aspects in project management. The presence of missing data (MD) in software attributes makes SDEE even more complex. K-nearest neighbors imputation (KNNI) has been widely used in SDEE to deal with the MD issue. However, KNNI, in its classical process, has low tolerance to imprecision and uncertainty especially when dealing with categorical features. When dealing with categorical attributes, KNNI uses a classical approach, employing mainly numbers or classical intervals to represent software attributes and similarity measures originally designed for numerical attributes. ObjectivesThis paper evaluates the use of an optimized fuzzy clustering-based KNNI (FC-KNNI) and compares it with classical KNN when dealing with mixed data in the context of SDEE. MethodsWe investigate the effect of two imputation techniques (FC-KNNI and KNNI) on five SDEE techniques: case-based reasoning, fuzzy case-based reasoning, support vector regression, multilayer perceptron, and reduced-error pruning tree. The evaluation is carried out using six publicly available datasets for SDEE using two performance measures, standardized accuracy (SA), and Pred (0.25). The Wilcoxon statistical test is also performed to assess the significance of results. ResultsThe results are promising in the sense that using an imputation technique designed for mixed data is better than reusing methods originally designed for numerical data. We found that FC-KNNI significantly outperforms KNNI regardless of the SDEE technique and dataset used. Another important finding is that F-CBR improved the analogy process compared to CBR. ConclusionThe introduction of fuzzy sets and fuzzy clustering in the analogy process improves its performances in terms of SA and Pred (0.25).