When service-based applications implement business processes, it is important to monitor their performance in terms of Key Performance Indicators (KPIs). If monitoring results show that the KPIs do not reach target values, the influential factors have to be analyzed and corresponding adaptation actions have to be taken. In this paper we present a novel adaptation approach for service-based applications (SBAs) based on a process quality factor analysis. This approach uses decision trees for showing the dependencies of KPIs on process quality factors from different functional levels of an SBA. We extend the monitoring and analysis approach and show how the analysis results may be used to come up with an adaptation strategy leading to an SBA that satisfies KPI values. The approach includes creation of a model which associates adaptation actions to process quality metrics, extraction of adaptation requirements based on analysis results, and identification of an adaptation strategy which can consist of several adaptation actions on different functional levels of an SBA.