Discovering the critical number of respondents to validate an item in a questionnaire: the binomial cut-level content validity proposal

The question that drives this research is: “How to discover the number of respondents that are necessary to validate items of a questionnaire as actually essential to reach the questionnaire’s proposal?” Among the efforts in this subject, Lawshe (Pers. Psychol 28:563–575, 1975), Wilson et al. (Meas. Eval. Couns. Dev. 45:197–210, 2012), Ayre and Scally (Meas. Eval. Couns. Dev. 47:79–86, 2014), Lynn (Nurs. Res. 35:382–386, 1986); Polit et al. (Res. Nurs. Health 30:459–467, 2007) approached this issue by proposing the Content Validation Ratio (CVR) and Content Validations index (CVI) proportion that look to identify items that must be relevant or even essential in a questionnaire. Despite their contribution, these studies do not check if an item validated as “essential” should be also validated as “not essential” by the same sample, which should be a paradox. Another issue is the the loss of nuance caused by assigning a probability equal to 50% to a item be randomly checked by a respondent as essential, despite the rater has three or more options to choose. Our proposal faces these issues, making it possible to verify if a paradoxical situation occurs, and being more precise in recommending whether an item should either be retained or discarded from a questionnaire.