details of content validity and objectifying it in instrument development

background & aim : researchers in the nursing science study complex constructs for which valid and reliable instruments are needed. when an instrument is created, psychometric testing is required, and the first-step is to study the content validity of the instrument. this article focuses on the process used to assess the content validity. methods & materials : this article examines the definition, importance, conceptual basis, and functional nature of content validity in instrument development. the conditional and dynamic nature of content validity is discussed, and multiple elements of content validity along with quantitative and qualitative methods of content validation are reviewed. results : in content validity process, content representativeness or content relevance of the items of an instrument is determined by the application of a two-stage (development and judgment) process. in this review, we demonstrate how to conduct content validity process, to collect specific data for items generation and calculation of content validity ratio, content validity index, modified kappa coefficient, and to guide for interpreting these indices. face validity through suggestions of expert panel and item impact scores is also discussed in paper. conclusion : understanding content validity is important for nursing researchers because they should realize if the instruments they use for their studies are suitable for the construct, population under study, and sociocultural background in which the study is carried out, or there is a need for new or modified instruments.