The Big Five Inventory (John et al., 1991) is a commonly used questionnaire, with high test-retest reliability (Cobb-Clark & Schurer, 2012). Because of its reliability, and because our personalities are relatively stable (McCrae & Costa, Jr., 1994), our results will be similar across time. Inter-rater reliability is important, especially in observational research, to ensure consistency and objectivity in the conclusions being drawn (Goodwin & Goodwin, 2017).

Validity is important as it ensures that we are measuring what we want to measure. Predictive validity suggests that our measure will accurately predict future behaviours. Using the example of the Big Five, we could predict that a participant who scores higher on extraversion would be more likely to attend a large party than someone who scored lower on extraversion. In this scenario, we would be operationally defining someone who is more extraverted as someone who is more likely to attend a large social gathering. Operational definitions are a form of construct validity, which provides us with a way of measuring something that cannot be quantifiably measured, such as a personality trait.

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References

Cobb-Clark, D. A., & Schurer, S. (2012). The stability of big-five personality traits. Economics Letters, 115(1), 11-15.https://doi.org/10.1016/j.econlet.2011.11.015

Goodwin, K. A., & Goodwin, C. J. (2017).Research in psychology: Methods and design(8th ed.). John Wiley & Sons, Inc.

John, O. P., Donahue, E.M., & Kentle, R. L. (1991). Big Five Inventory (BFI) [Database record]. APA PsycTests.https://doi.org/10.1037/t07550-000