Chapter 41 - A practical approach to the assessment and quantification of content validity

Abstract

The assessment of content validity is important when developing instruments used to measure complex phenomena and constructs, in pharmacy practice and health services research. Content validity provides evidence about the degree to which elements of an assessment instrument are relevant to and representative of the targeted construct for a particular assessment purpose. This chapter investigates the elements of content validity, describes key stages of conducting the content validity evaluation, provides a practical approach for assessing content validity, and discusses various content validity indices. During the assessment of content validity, a panel of experts evaluates instrument elements and rates them based on their relevance and representativeness to the content domain. The three-step process involves: (1) the development stage, (2) judgment and quantifying stage, and (3) revising and reconstruction stage. Several quantifying indices are discussed in this chapter, including the content validity ratio (CVR), content validity index (CVI), modified–Kappa, and some agreement indices. Use of these indices is very important, especially when the instrument is used to measure health outcomes or to guide clinical decision making. The assessment of content validity should be undertaken with the same methodological rigor as other elements of the psychometric testing of instruments.