A survey with a limited denominator

A fictional school magazine receives this Portuguese report: «Convidámos 200 alunos a responder. Participaram 80 pessoas e 60 delas apoiam uma sala tranquila durante o intervalo». A comment adds: «O resultado diz respeito a quem respondeu; não conhecemos a opinião dos restantes». The proposed headline instead says: «75 por cento da escola exige uma sala nova imediatamente». There is no information about the 120 nonrespondents, available rooms or project costs. The language task asks the learner to identify the report’s limitation, explain the headline’s overstatement and propose a faithful alternative. The school contains exactly the 200 invited students in this invented exercise. The writer may later argue for studying the project, but that judgment must be distinguished from what the survey measured. None of these figures describes a real school or an actual national survey.