Quality can determine a software product's success or failure in today's competitive market. Among the many characteristics of quality, some aspects deal directly with the functional correctness or the conformance to specifications, while others deal with usability, portability, and so on. Correctness - that is, how well software conforms to requirements and specifications - is typically the most important aspect of quality, particularly when crucial operations depend on the software. Even for market segments in which new features and usability take priority, such as software for personal use in the mass market, correctness is still a fundamental part of the users' expectations. We compare and classify quality-evaluation models, particularly those evaluating the correctness aspect of quality, and examine their data requirements to provide practical guidance for selecting appropriate models and measurements.