Two case studies in measuring software maintenance effort

In this paper we present the results of two measurement programs, that were aimed at investigating possible cost drivers for software maintenance. The two measurement programs were implemented in the software maintenance departments of two different organizations. Both programs were set up in roughly the same way. We use standard statistical techniques-principal component analysis and multiple regression analysis-to analyse the datasets. Surprisingly, with one of the datasets we are able to explain a fair amount of variance in the effort, while with the other dataset we can explain much less. From a closer inspection of the different environments we conjecture that the existence of a consistently applied process is an important prerequisite for a successful measurement program. In addition, if the process exists in multiple variants, it is important to know which variant is applied when.