To define some concept of study in such a way that it can be observed and measured. For example, "well being" might be measured by asking people to rate their overall satisfaction with their life style, or "anti-social behaviour" might be measured by frequency of arrest or criminal prosecution.
A study to be operationally defined requires that we first specify our constructs; developing reliable and valid operations is the last step of specifying constructs when we are designing our own studies.
The science of psychology tries to develop explanations of human behavior through objective observations. The procedures or operations that we use to objectively measure variables are known as its operational definition. The operational definition gives the variable meaning within a particular study. The features of a operational definition vary depending on the study design.
Operational Definitions Operationally Defined - Stuart C. Dodd, Ethel Shanas - The American Journal of Sociology, Vol. 48, No. 4 (Jan., 1943), pp. 482-491 - Abstract: This paper attempts to meet the challenge of defining operational definitions operationally. A definition is operational to the extent that it specifies the procedure for identifying or generating the definiendum and finds high reliability for the definition. The logical form of this definition, its gradational phrasing, the concepts of "procedure" and "reliability," and the two types of operational definitions are commented upon.
Operationally Defined - Stuart C. Dodd
The Public Opinion Quarterly, Vol. 15, No. 3 (Autumn, 1951), pp. 547-556
Abstract: Moment formulas can be used as an aid in defining important human ideals and values in measurable terms. Such classic ideals as "liberty, equality, and fraternity" can be redefined as a moment of some one order.
Expression profile of an
operationally-defined neural stem cell clone. - Parker MA, Anderson JK, Corliss
DA, Abraria VE, Sidman RL, Park KI, Teng YD, Cotanche DA, Snyder EY.
Abstract: ESCs, HSCs, and operationally-defined NSCs, all of which have been identified not only by markers but by functional assays in their respective systems and whose state of differentiation could be synchronized, shared a large number of genes. Although the most stem-like genes were expressed by ESCs, NSCs and HSCs shared a number of genes. CNS-derived neurospheres, on the other hand, expressed fewer stem-like genes held in common by the other operationally-defined stem cell populations. Interestingly, when the operationally-defined NSC clone was cultured as a neurosphere, its expression pattern shifted from a stem-like pattern towards a more differentiated one, suggesting that the neurosphere, without functional validation, may be a poor model for predicting stem cell attributes because it consists of heterogeneous populations of cells, only a small proportion of which are truly stem-like. Furthermore, when operationally defined, a common set of stem-like genes does emerge across both embryonic and somatic stem cells of various organ systems, including the nervous system.