## 5 Application and Success Evaluation  
Then application and success evaluation was executed. This was done by expert evaluation in the form of questionnaires and semi-structured interviews on the one hand and performance measurements based on data from the case study projects on the other hand. The questionnaires were designed under consideration of guidelines by [PERSON] [65] and handed out personally to six experts: Three end-users of the support within the case study projects as well as the three case study project leaders. All participants come from the field of mechanical engineering or industrial engineering and work in the development of additively manufactured products. The six questionnaires are analyzed, consisting of 49 questions with different question types in the following areas:  
* Personal background. * Requirement changes (general). * Method for systematic assessment of requirement change risk. * Software prototype. * Future research potentials. (detailed results see Appendix A)  
Information for both application evaluation as well as success evaluation was gained by the questionnaires. Afterwards one interview per case study (60-90 min) was conducted with participants. In preparation of the interviews, the questionnaires were analyzed to identify open issues and discrepancies. Those were discussed and elaborated. Additionally, the interviews were used to gather more open-ended feedback. No objective data on requirement changes was available in the partner companies beforehand (Sections 1 and 4). Therefore, the case study projects are used to systematically document requirement changes and create a database for application evaluation. Based on a template, practitioners captured information about each change like change causes, change occurrence, change impact and management of the change throughout the case study project. This database was used to assess accuracy of support results. Analysis of the questionnaires and interviews led to the overall result, that the developed method and software prototype target an existing demand for aid in managing requirement changes from a risk perspective and helps to reduce inefficiencies from those. Mainly, by identifying high risk requirements and sensitize developers to consider risk of requirement changes in general and for critical requirements in particular. Additionally, it helps to improve the identification of dependencies across departments/disciplines and communication within the development team. An in-depth analysis for the case study \"control cam\" revealed that requirement changes of requirements assessed as high risk led to additional development effort of 176 work hours. Those changes came from better understanding of the problem space by the customer and could have been addressed by risk management actions. After deducting the application effort of the support, users estimated potential savings to about 130 work hours. Although this estimate was insecure, it was consistent with findings from the other case studies and indicates the potential leverage of risk assessment and subsequent risk management for requirement changes. Change documentation from case studies also showed, that besides requirement changes the addition of new requirements triggers iterations and thereby causes additional effort to adapt the requirement set and the current solution. With regard to the first research question RQ1, the method for risk assessment was considered appropriate. The generalization by using the main feature list and an FMEA logic as well as the three defined priority categories are sufficient. The results of assessment are reasonable and accurate, but strongly depend on the underlying database and therefore the quality of results might vary. This leads to a mixed rating. Due to the ongoing improvement of this database in the course of usage (Section 4) this was expected for initial application. Presumably, the quality of results will increase with experts' gaining experience and requirement change data was continuously integrated into the database.