Operational Definition

An operational definition is a demonstration of a process – such as a variable, term, or object – in terms of the specific process or set of validation tests used to determine its presence and quantity. The term was coined by Percy Williams Bridgman (see Operationalization). Properties described in this manner must be sufficiently accessible, so that persons other than the definer may independently measure or test for them at will.[citation needed] An operational definition is generally designed to model a conceptual definition. The most operational definition is a process for identification of an object by distinguishing it from its background of empirical experience. The binary version produces either the result that the object exists, or that it doesn't, in the experiential field to which it is applied. The classifier version results in discrimination between what is part of the object and what is not part of it. This is also discussed in terms of semantics, pattern recognition, and operational techniques, such as regression.

For example, the weight of an object may be operationally defined in terms of the specific steps of putting an object on a weighing scale. The weight is whatever results from following the measurement procedure, which can in principle be repeated by anyone. It is intentionally not defined in terms of some intrinsic or private essence. The operational definition of weight is just the result of what happens when the defined procedure is followed. In other words, what's being defined is how to measure weight for any arbitrary object, and only incidentally the weight of a given object.

Operationalize means to put into operation. Operational definitions are also used to define system states in terms of a specific, publicly accessible process of preparation or validation testing, which is repeatable at will. For example, 100 degrees Celsius may be crudely defined by describing the process of heating water until it is observed to boil. An item like a brick, or even a photograph of a brick, may be defined in terms of how it can be made. Likewise, iron may be defined in terms of the results of testing or measuring it in particular ways.

One simple, every day illustration of an operational definition is defining a cake in terms of how it is prepared and baked (i.e., its recipe is an operational definition). Similarly, the saying, if it walks like a duck and quacks like a duck, it must be some kind of duck, may be regarded as involving a sort of measurement process or set of tests (see duck test).