Operational Definitions of Variables

Operational Definitions

An operational definition specifies how to measure a variable so that you can assign someone a score such as high, medium, or low social power. For example, we might refer to an organizational chart to count how many subordinates an individual has. Operational definitions are the means by which we obtain the numbers or categories for the variables. That is, an operational definition is the sequence of steps or procedures research follows to obtain a measurement. The variable may have only two possible scores such as present and absent or high and low, or it may have 100 or more possible scores, as with IQ tests. Provided there are at least two possible scores or levels, it is a variable and the operational definition is at least minimally useful.

These terms must have empirical referents (that is, we must be able to count, measure, or in some other way gather the information through our senses). Whether the object to be defined is physical (e.g ., a machine tool) or highly abstract (e.g ., achievement motivation), the definition must specify characteristics and how they are to be observed. The specifications and procedures must be so clear that any competent person using them would classify the objects in the same way.

In the philosophical study of the meaning and use of definitions, three types of definitions have been isolated: real definitions, nominal definitions, and operational definitions. The aim of a real definition is to capture the ultimate or essential nature of the actual phenomenon in question. One example of a real definition would be the mathematical definition of a triangle as a three-sided figure. A nominal definition, that specified the meaning and component of the term for the purposes of rigorous philosophical inquiry.

Operational definitions (Baker uses this term as operationalizing definitions) may vary, depending on your purpose and the way you choose to measure them. Here are two different situations requiring different definitions of the same concepts.

1. Survey
You conduct a survey among students and wish to classify their answers by their class levels. You merely ask them to report their class status, and you record it. In this case, class is freshman, sophomore, junior, or senior and you accept the answer each respondent given as correct. This is a rather casual definition process but nonetheless an operational definition. It is probably adequate in this case even though some of the respondents report inaccurately.

2. Measurement
You make a tabulation of the class level of students for the university registrar's annual report. The measurement task here is more critical, so your operational definition needs to be more precise. You decide to define class levels in terms of semester hours of credit completed by the end of the spring semester and recorded in each student's record in the registrar's office.

Those examples deal with relatively concrete concepts, but operational definitions are even more critical for treating abstract ideas. Suppose one tries to measure a construct called "organizational commitment." We may intuitively understand what this means, but attempting to measure it among workers is difficult. We would probably develop a commitment scale, or we may use a scale that has already been developed and validated by someone else. This scale then operationally defines the construct.

While operational definitions are needed in research, they also present some problems. One ever-present danger is thinking that a concept and its operational definition are the same things. We forget that our definitions provide only limited insight into what a concept or construct really is. In fact, the operational definition may be quite narrow and not at all similar to what someone else would use when researching the same topic. When measurements by two different definitions correlate well, the correlation supports the view that each definition adequately measures the same concept.

The problem of operational definitions is particularly difficult when dealing with constructs. Constructs have few empirical referents by which to confirm that an operational definition really measures what we hope it does. The correlation between two different definition formulations strengthens the belief that we are measuring the same thing. On the other hand, if there is little or no correlation, it may mean we are tapping several different partial managing of a construct. It may also mean one or both of the operational definitions are not true labels.

Whether you use a definitional or operational definition, its purpose in research is basically the same-to provide an understanding and measurement of concepts. We may need to provide operational definitions for only a few critical concepts, but these will almost always be the definition used to develop the relationships found in hypotheses and theories.