Which testing principle is being applied when more testing is directed to areas with more defects than average?

The principle that is applied when more testing is directed to areas with more defects than average is known as defects cluster together. This principle is based on the observation that in many software systems, a significant number of defects are found in a small number of modules or components. As a result, allocating more testing resources to those areas where defects have previously been identified can help uncover more issues and improve the overall quality of the software.

By focusing on areas that historically have a higher defect density, testers can strategically target their efforts to maximize the effectiveness of the testing process. This targeted approach not only makes testing more efficient but also helps in identifying and addressing potential problems before they can affect end users.

The other mentioned principles provide valuable insights into different aspects of software testing; however, they do not specifically address the rationale for concentrating testing efforts based on past defect occurrence.