In planning software process improvement activities, it is essential to determine the factors that most influence the success of a software project. In this article, we present an investigative and analytical framework for evaluating software process factors based on the Goal/Question/Metric (GQM) paradigm. We built descriptive models of the software process, defects, and cost. These models were used as a common basis of quantitative analysis in the study. We also developed evaluative models that clarify the relationship between the basic metrics, the analysis method, and the goals of the analysis. We confirmed the usefulness of our analytical framework, by applying it in an actual development environment at Matsushita Communication Industrial Company in Japan, where we studied four communications-software projects. This article reports the patterns we noted in the data and suggests process improvement activities based on those findings.