ITU-T Recommendation P.800 provides methods and procedures for conducting subjective evaluations of transmission quality. The main revision includes an annex describing the Comparison Category Rating (CCR) procedure, aligning with recent revisions of Recommendation P.830. The document covers various testing methods such as conversation-opinion tests, listening-opinion tests, interview and survey tests, and other specialized tests. It emphasizes the importance of realistic test conditions, proper setup, and detailed data collection and analysis. The recommended methods are applicable to a wide range of degradation factors, including loss, noise, transmission errors, and environmental noise. The document also provides guidelines for preparing speech material, processing it, and conducting experiments, including the use of specific opinion scales and statistical analysis techniques.ITU-T Recommendation P.800 provides methods and procedures for conducting subjective evaluations of transmission quality. The main revision includes an annex describing the Comparison Category Rating (CCR) procedure, aligning with recent revisions of Recommendation P.830. The document covers various testing methods such as conversation-opinion tests, listening-opinion tests, interview and survey tests, and other specialized tests. It emphasizes the importance of realistic test conditions, proper setup, and detailed data collection and analysis. The recommended methods are applicable to a wide range of degradation factors, including loss, noise, transmission errors, and environmental noise. The document also provides guidelines for preparing speech material, processing it, and conducting experiments, including the use of specific opinion scales and statistical analysis techniques.