4.8: Summary of Measuring Variables

Key Takeaways

• Measurement is the assignment of scores to individuals so that the scores represent some characteristic of the individuals. Measurement of behavior can be achieved in a wide variety of ways.
• Psychological constructs such as intelligence, self-esteem, and depression are variables that are not directly observable because they represent behavioral tendencies or complex patterns of behavior and internal processes. An important goal of scientific research is to conceptually define psychological constructs in ways that accurately describe them.
• For any conceptual definition of a construct, there will be many different operational definitions or ways of measuring it. The use of multiple operational definitions, or converging operations, is a common strategy in psychological research.
• Variables can be measured at four different levels—nominal, ordinal, interval, and ratio—that communicate increasing amounts of quantitative information. The level of measurement affects the kinds of statistics you can use and conclusions you can draw from your data.
• Psychological researchers do not simply assume that their measures work. Instead, they conduct research to show that they work. If they cannot show that they work, they stop using them.
• There are two distinct criteria by which researchers evaluate their measures: reliability and validity. Reliability is consistency across time (test-retest reliability), across items (internal consistency), and across researchers (interrater reliability). Validity is the extent to which the scores actually represent the variable they are intended to.
• Validity is a judgment based on various types of evidence. The relevant evidence includes the measure’s reliability, whether it covers the construct of interest, and whether the scores it produces are correlated with other variables they are expected to be correlated with and not correlated with variables that are conceptually distinct.
• Once you have used a measure, you should reevaluate its reliability and validity based on your new data. Remember that the assessment of reliability and validity is an ongoing process.
• In addition to self-report measures, behavior can also be measured physiologically or through unobtrusive methods.
• The Hawthorne effect, which occurs when research participants alter their behaviors because they know they are being studied, is not a risk in unobtrusive research as it is in other methods of data collection.

What's Next?

As this textbook is designed, this is the end of Unit 1 (Introduction to Research Methods). Now that you have a sense of some of the technical definitions, you have a basis to start reading academic research and then to start designing y our own research. The second unit will focus on research articles. It will include information to help you find, read, and understand empirical research articles, as well as instructions on formatting your own research reports.

Exercises

• Practice: Complete the Rosenberg Self-Esteem Scale and compute your overall score.
• Practice: Think of how you could measure a construct like jealousy using each of the following types of operational definitions:
  • Self-report (survey, interview, focus group)
  • Psychobiological measure
  • Unobtrusive measure (observation, physical trace, archival record)
• Practice: Think of how you could measure a construct like depression using each of the following types of operational definitions:
  • Self-report (survey, interview, focus group)
  • Psychobiological measure
  • Unobtrusive measure (observation, physical trace, archival record)
• Practice: Think of how you could measure a construct like wealth using each of the following types of operational definitions:
  • Self-report (survey, interview, focus group)
  • Psychobiological measure
  • Unobtrusive measure (observation, physical trace, archival record)
• Practice: Ask several friends to complete the Rosenberg Self-Esteem Scale. Then assess its internal consistency by making a scatterplot to show the split-half correlation (even- vs. odd-numbered items). Compute the correlation coefficient too if you know how.
• Discussion: Think back to the last college exam you took and think of the exam as a psychological measure. What construct do you think it was intended to measure? Comment on its face and content validity. What data could you collect to assess its reliability and criterion validity?
• Practice: Think of how you could unobtrusively measure