To capture information about the needs of stakeholders and the problem domain and to specify the requirements of planned software, developers can use several elicitation techniques from various sciences such as the social sciences or psychology. Each technique has different performance depending on the context in which it is applied. Therefore, to know which requirements elicitation technique is the most appropriate, it is necessary to understand the meaning of appropriate technique. Practitioners and researchers have differing views of the techniques suitability. This paper proposes a model to represent the appropriateness of elicitation techniques. The model uses an estimator calculated through the variables of requirements quantity and quality. To illustrate the proposal, it was validated with data from an experiment found in the related literature. Our work aims to unify an appropriateness construct, which can help standardize future empirical studies and thus facilitate the creation of a body of knowledge on requirements elicitation techniques.