The Student Evaluation of Teaching (SET) instrument provides insight for instructors and administrators alike, often touting high response-rates to endorse their validity and reliability. However, response-rate alone omits consideration for adequate quantity of ‘observational sampling opportunity’ (OSO) data points (e.g., high student attendance). The current paper endorses that quantity of OSO data points is critical to validity/reliability of longitudinal SET paradigms. It is reasoned ethically-challenged to rely on SET via basic surface-measures such as simple ‘response-rate’, when specific higher-quality data reflecting adequate quantity of OSO data points, can be filtered for from the same dataset. In addition, ethical concerns regarding the gauging of teaching performance via quantitative data analyses applied to inappropriate categorical/nominal response data, is also discussed.