To do this it must also then convert concepts into variables . This process is called operationalization. Operationalization is taking a theory with concepts and converting it to an hypothesis with variables. An hypothesis states a theory in a way that makes it testable. In order for an hypothesis to be testable, we need variables that are measurable.
Variables are measures or indicators of the concepts.
Variables are called variables because they vary across the people we study. To operationalize a concept is to make it measurable by converting it into a variable. Some concepts are easy to operationalize, such as age, earnings, years of formal schooling, etc. Others might be more controversial such as race. We might operationalize self-esteem by measuring it according to responses people give to survey questions about how they perceive themselves.