The following chapter is excerpted from Designing HIV/AIDS Intervention Studies: An Operations Research Handbook, Andrew Fisher and James Foreit, 2002, Washington, DC: Population Council. (More on OR Handbook)
A fter formulating the study objectives and hypotheses and describing fully the study intervention, the next step in the research process is to define operationally the key variables and terms of the study. Operational definitions serve two essential purposes: (1) They establish the rules and procedures the research investigator will use to measure the key variables of the study, and (2) they provide unambiguous meaning to terms that otherwise might be interpreted in different ways. Every research proposal must include operational definitions of major variables and terms.
Operational Definitions of Variables
Suppose that a dependent variable of a study is knowledge about how HIV/AIDS is transmitted. Before this variable can be measured, it is necessary first to establish the operational procedures that specify how the measurement will be made and at the same time define what the researcher means by the words “knowledge about how HIV/AIDS is transmitted.” This variable must be defined in terms of events that are observable by the senses and therefore measurable.
The observable events serve as an indicator of the variable, knowledge about HIV/AIDS transmission. Alone and by itself, knowledge is not observable by the senses. It is an abstract concept. You cannot touch knowledge, see it, smell it, taste it, or hear it. What is needed is an observable event that can be measured and that indicates knowledge. Usually, such an indicator of knowledge in an HIV/AIDS study is based on a series of questions. For example, you might ask a respondent, “Do you know how a person can become infected with AIDS?” “Please list all the ways you know a person can get AIDS.” “Can a...