Lecture 5.3: Finding and Devising Measures

I. What is an operational definition? Defining a concept in terms of the procedures used to either manipulate or measure it. It is an objective recipe for measuring or manipulating what we claim to be measuring/manipulating.

II. Finding a measure

A. The "term" approach

1. Identify likely names for the construct you want to measure.

2. Consult the thesaurus for Psychological Abstracts.

3. Search the literature via PsycLit or Psychological Abstracts.

4. The introduction, method, and reference sections of the articles you find will refer to sources of measures and to studies that provide evidence of the validity of those measures.

B. The "author" approach

1. Find names of researchers associated with your topic in a text book. If you're having trouble, use the thesaurus to identify your topic, then do a literature search for books and chapters on that topic.

2. Do computer or Psych Abstracts search by author's name.

3. The articles you find will refer to sources of measures and to studies that provide evidence of the validity of those measures.

C. The "sources" approach

Go to manuals that describe various measures, such as: Mental Measurement's Year Book, Test Critiques, or Measures of Personality and Social Psychological Attitudes.

III. Devising your own measure of a psychological construct

A. Be sure you know what you want to measure and what you don't. You can't expect to have a good operational definition of a poorly defined concept. Clearly, your measure must be consistent with your definition of the construct. Having a clear picture of what you want to measure can also help you determine how to establish the measure's:

convergent validity (what the measure should correlate with),

discriminant validity (what the measure might, but shouldn't, measure), and

content validity (what types of items to include).

B. How do you develop a clear idea of what you want to measure?

1. Dictionaries, reflection, reading, and theory can all help you develop a clear idea of what it is you want to measure--and what you don't want to measure. For example, a dictionary and a thesaurus can help you realize what related concepts you don't want to measure. Definitions from theory and dictionaries can also help you understand the key aspects of your construct that you must measure.

2. Theories may be especially useful because theories can tell you:

a. What the key dimensions of the construct are-- so that you can make sure that your measure taps all the key dimensions

b. How the construct can be measured--even if your measure doesn't use one of those ways, you can use these other ways of measuring the construct to validate your measure. Note that many measures and manipulations are judged to be valid simply because they are closely tied to theoretical definitions of the concept they are supposed to measure (e.g., Kohlberg's measure of moral development; Piaget's measures of cognitive development).

c. Whether the concept can be measured by using direct self-report questions

C. Decide what observable behavior you want to use as an indicator of your construct:

1. Physiological responses

2. Overt Actions

3. Verbal responses

D. Decide what aspect of the behavior to measure

1. Latency

2. Speed

3. Rate

4. Duration

5. Frequency

6. Errors/Accuracy

7. Intensity

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