Requirements validation is an important aspect for ensuring high quality software. During requirements validation not the software product is validated but the requirements themselves. Therefore, much effort is spent on manual validation activities. Commonly used are requirements inspections, where the specification is read from different persons assuming different roles or applying different reading techniques partly accompanied by checklists. Actual defect detection with requirements inspection is costly and defect detection rates must be considered low. Therefore, repeated validation is used or validation with multiple inspection groups - known as N-fold inspections. However, this does not only yield more defects found but also more false positives. In this paper, we investigate how defect aggregation can be used to improve the overall quality of validation. Therefore, we conducted an experiment with 22 N-fold inspection groups consisting of four to five reviewers each. Results show that simple aggregation of all results leads to a number of false positives that can actually negatively impact the validation task, while the use of more tailored aggregation strategies can considerably improve the validation of requirements with N-fold inspections.
