Which of the following is NOT a purpose of metrics in software testing?

Metrics in software testing serve various purposes, primarily focused on improving the testing process and providing insights into the quality of the software being tested. The purpose of metrics is to quantitatively assess different aspects of testing, such as workload, progress, quality, and effectiveness.

The option regarding the application to the RAD (Rapid Application Development) development model does not align with the typical purposes of metrics in testing. While RAD is a development methodology, metrics are generally designed to assess activities across various development processes rather than being specific to one model. The other options clearly represent valid purposes of metrics, such as tracking progress in test environment preparation, test case preparation, and milestone achievement, as they provide essential information on how effectively the testing is progressing and whether it is aligned with project timelines and goals.

Thus, the correct choice stands out because it does not directly relate to the foundational objectives of measurement and reporting that are characteristic of software testing metrics.