This is the 2007 version. Click here for the 2017 chapter 01 table of contents.

Distinguishing Operational Definitions, Variables, and Values

Throughout this book we will be referring to psychological variables. Some students do not have a grasp of the simple term variable, so this might be a good time to clarify the concept. A variable is some characteristic of the world that can vary or change. It is something that can be measured or detected. Therefore operational definitions , which define a word by telling how to measure or detect something, always define a variable.

What are variables? How do they relate to operational definitions? What is the difference between a variable and a value?

Variables are distinct from values -numbers or scores. Variables can take on many possible values, depending on what is measured. The following table shows examples of variables, operational definitions, and values.

Variables, operational definitions, and values

The last definition in the table (number of hairs on the left thumb) reminds us that operational definitions are not always good or valid. They are simply descriptions of measurement actions. You could argue that the last definition is an operational definition. It implies a set of measurement oper­ations (look at left thumb, count hairs) but it is not a good definition if you want to measure intelligence. The second and third definitions also are poor because they are poorly specified (which questionnaire? what repair?) Do not assume an operational definition is valid, just because a researcher has generated a number with it.

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