Health behavior and health education research often depend on the measurement of abstract constructs and concepts. In these cases, measurement must be extended to in- clude the process of converting abstract concepts into empirical indicators—the actual methods or instruments used to measure the concepts. Empirical indicators can include
FIGURE 6.1. STEPS IN THE SCALE DEVELOPMENT PROCESS.
Concept analysis
Revision
Validity assessment
Item writing
Reliability assessment
Item analysis Concept
identification
Content validity
Final scale
any of the instruments we presented in Chapter Two (for example, self-report ques- tionnaires, observations, chart reviews, and physiological measures).
In behavioral research, scale development begins with a thorough understand- ing of the concept to be measured. The measurement process then proceeds to writ- ing the items, stating the rules for using the scale, and devising scoring methods.
The measurement process concludes with the assignment of a numeric score, gen- erally corresponding to the type of conceptual dimensions or the amount (quantity) of the variable. We arrive at the numeric score through established rules and scor- ing methods. Figure 6.2 depicts the measurement process in health behavior research and evaluation. (As with any form of measurement, error is an undesirable but ex- pected component.)
Gibbs’s Model
As a student in public health, you have had some exposure to the predominant theo- ries explaining health behavior, its antecedents, and its outcomes. These theories include:
• Health belief model (Rosenstock, 1960)
• Theory of planned behavior (Ajzen, 1991)
• Social cognitive theory (Bandura, 1997)
• Transtheoretical model (Prochaska & DiClemente, 1982)
• Diffusion of innovation (Rogers, 1995)
• Stress and coping theory (Lazarus & Folkman, 1984)
Each theory or model proposes a set of concepts (for example, perceived barriers and benefits, subjective norms, self-efficacy, OE, stress, and coping), and each proposes ways in which the concepts work together to determine or explain health behavior or other aspects of health. We refer to the associations among concepts proposed within the theory as relational statements (Gibbs, 1972). These associations are often depicted by using arrows to link related concepts. The arrow links the concept considered to be the cause (or the one that logically precedes the concept that follows it) to the con- cept considered to be the outcome (or the one that follows the first concept). For ex- ample, social cognitive theory (SCT) states that people who have higher levels of self-efficacy and more positive OE related to a particular behavior are more likely to engage in that behavior.
Behavioral theorists tend to use terms for concepts that fail to indicate exactly what quantity the concept measures (Mulaik, 2004). Thus an important next step is to state the concept as a variable in quantifiable terms. For example, if the self-efficacy
FIGURE 6.2. THE MEASUREMENT PROCESS IN HEALTH BEHAVIOR RESEARCH.
Theoretical concept
Empirical indicator
Numerical score
Error
variable is “the degree to which one feels self-efficacious in performing a breast self-examination,” OE might be “degree to which one expects positive outcomes from performing a breast self-examination,” and breast self-examination might be “how often one performs a breast self-examination.” Figure 6.3 depicts these relationships among variables. The two relational statements are
1. Women who report higher degrees of self-efficacy for performing breast self- examination will report more frequent breast self-examinations.
2. Women who report more positive OE related to performing breast self-examinations will report more frequent breast self-examinations.
If we want to test these theoretical associations, we must first understand and de- fine the concepts—self-efficacy, outcome expectations, and breast self-examination. Then we must develop instruments to measure the concepts. The process whereby an inves- tigator defines a concept in theoretical terms and then makes decisions as to how to mea- sure it empirically is called a transformational statement (Gibbs, 1972). After researchers develop the instrument, they next devise rules to assign a numeric score that adequately reflects the amount of the concept possessed. Figure 6.4 illustrates the entire process, as proposed by Gibbs (1972), using terms later modified by Dulock and Holzemer (1991).
We give relational statements different names (that is, axiom, proposition, theorem, and hypothesis) at each level of the model depicting the relationship. As noted in the model, higher-level constructs might be transformed into lower-level concepts before the selection or development of measurement tools. Each concept must be transformed into an empirical indicator and stated as a variable in order to collect empirical data.
Finally, a set of rules and procedures must be created in order to arrive at a numeric score that can be used in statistical analysis.
As shown in Figure 6.4, we can divide Gibbs’s model into a conceptual component and an empirical component, and the transformational statement serves as a bridge be-
Degree of self-efficacy for
performing breast self-examination
Frequency of breast self-examination Degree to which person expects
positive outcomes of breast self-examination
FIGURE 6.3. EXAMPLE OF RELATIONAL STATEMENTS IN SOCIAL COGNITIVE THEORY.
tween the two components. Within the conceptual component, relationships between concepts are presented in abstract terms. For example, we might say that the concept of self-efficacy is associated with the health behavior of breast self-examination. The relational statement might be that women who report higher degrees of self-efficacy for performing a breast self-examination will report more frequent self-examinations.
However, in the empirical part of the model, we are concerned with exactly how to measure each concept. Our concerns here are (1) the type of measuring instrument needed to measure the concepts and (2) how we will assign numeric scores using our measuring instruments. For our example, we might choose self-report measures in which we first ask women to rate, using a ten-point scale, how confident they are about per- forming a breast self-examination and then ask how often they performed the behav- ior in the past year. We then assign numeric scores to the responses, using predetermined FIGURE 6.4. GIBBS’S RELATIONAL MODEL (1972) AS MODIFIED
BY DULOCK AND HOLZEMER (1991).
Construct Axiom Construct
Concept Proposition Concept
Empirical
Indicator Theorem Empirical
Indicator
Score Hypothesis Score
Theoretical
Transformational Statement
Empirical
Transformational Statement
Source: Permission from J. Gibbs (2004).
rules. We use the numeric scores to perform statistical tests and the results of the statistical tests to determine whether a statistically significant positive correlation ex- ists between the scores on the self-efficacy measure and the scores on the breast self-ex- amination measure. If one does exist, we have evidence to support the theoretical statement that there is a positive relationship between the degree of self-efficacy to per- form breast self-examinations and the frequency of breast self-examination.
Theoretical and Operational Definitions
As with everything in measurement, we must provide precise definitions of our con- cepts. Two terms important in the measurement process are theoretical definitions and op- erational definitions. A theoretical definition is one in which the meaning of the concept (or construct) is given by substituting other words or phrases for it (Waltz, Strickland, et al., 1991). To locate a theoretical definition, when possible we turn to the theorist who first defined the term. For example, Bandura (1997, p. 3) defined self-efficacy as
“belief in one’s capabilities to organize and execute the course of action required to attain a goal.” And Ajzen (1991, p. 183) defined perceived behavioral control as “peo- ple’s perception of the ease or difficulty of performing the behavior of interest.” For a term that is not embedded in a particular theory or for which the origin is not known, we look to those who have written extensively about the concept. Among these terms are self-esteem and pain. For example, Rosenberg (1965, p. 15) is known for his work on self-esteem and defined the term as a “favorable or unfavorable opinion of oneself,” an evaluation of one’s worth. If we want to provide a theoretical definition of the con- cept of pain, we might use the definition provided by Gaston-Johnson, Fridh, and Turner-Norvell (1988), who noted that pain is a multidimensional subjective experi- ence of discomfort composed of both sensory and affective components.
Although theoretical definitions are useful in the conceptual phrase of a study, they fail to tell us exactly how a concept will be measured in a particular study. Thus, the process of transformation includes defining the concept in the way in which it will be measured for a specific study. We refer to this type of definition as an operational (or empirical) definition, and it is the definition of the concept in terms of the manner in which it will be measured (Nunnally & Bernstein, 1994). That is, it is stated in terms of the empirical indicators that we will use to measure the concept.
Operational definitions for the concepts of self-efficacy, self-esteem, and pain might be as follows:
Self-efficacy to quit smoking will be measured by the smoking cessation self- efficacy scale.
Self-esteem will be measured by the Rosenberg Self-Esteem Scale.
Pain intensity will be measured by using a visual analog scale representing a continuum of intensity from no pain to pain as bad as it can be.
The term operationalization is the transformation statement found in Gibbs’s model.
Like the transformational statement, operationalization is the process of transform- ing a concept from an abstract indicator into an empirical indicator. The opera- tionalization process includes making decisions about the way a concept will be measured, selecting the empirical indicators to be used to communicate its meaning, and selecting the procedures for measuring. In this process, based on theoretical and empirical work, the researcher or evaluator seeks to understand the meaning of the concept and the best approach to measure the concept for a specific study. Usually re- searchers operationalize a concept for a specific study. Two researchers might employ the same theoretical definition of a concept but choose different empirical indicators of the concept. Thus, we find operational definitions generally more restrictive and situation-specific than theoretical definitions.