Best Rating Scale Design Theory: Implications for Developing Questionnaires in Nursing and Health Sciences

Abstract

Several nurse researchers do not consistently engage the best rating scale design in developing health research questionnaires thus obscuring the obligatory psychometric properties of the tools as objective rating scales. In response, this paper intends to simplify the Rasch techniques of best rating scale (or questionnaire) validation into four stages. Among researchers and psychometricians, presenting the objective psychometric properties of questionnaires used as rating scales are the cornerstones of the mathematical credibility of any reading generated by the scale. On the contrary, being too reliant on the conventional methods called the classical test theory (CTT), most already “developed” questionnaires rarely display objective indices of the measuring tools. CTT is not the best method for designing questionnaires because its techniques rely on too many unproven mathematical assumptions. Correspondingly in this paper, the Rasch techniques of rating scale design are simplified into four steps for designing questionnaires as objective rating scales. A key contribution of Rasch validation technique is that essential psychometric properties are tested and displayed rather than merely assumed. Therefore, nurse researchers ought to show methodological and mathematical rigours aimed at designing questionnaires as objective measuring tools of health variables. Embracing the four phases of questionnaire design in Rasch techniques provides an easy-to-follow and scientifically robust framework for developing a questionnaire. Finally, the CTT approach to developing questionnaires lack evidence expected of an objective rating scale. Therefore, the four steps in Rasch techniques of questionnaire design, outlined here, present the techniques that researchers may engage in to minimise measurement errors.