Job performance aids (JPAs) have been studied in a variety of disciplines and for many different types of tasks, yet this is the first known research experiment using JPAs in the quality assurance (QA) context. The objective was to assess whether a JPA has an effect on the performance of a QA observer in the concurrent dual verification construct using a simple checklist for a basic assembly task. Results show that the JPA has only a limited effect, however there were three significant findings that may draw interest from a variety of practitioners. First, a novel testing methodology sensitive enough to measure the effects of a JPA on performance was created. Second, the discovery that there are different probabilities of detection for different types of error and their impact on the QA context may be the most far-reaching result. Third, these results highlight the limitations of concurrent dual verification as a control against defects.