What is operationalization?
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A definition of a concept (variable) in terms of the techniques (operations) used to measure same. In other words, it is a translation of an abstract concept (variable) into concrete and measurable terms (Cozby, 2009).
Example: The goal of this fictitious study is to investigate the effects of helping others (mentoring) on happiness using the pretest-posttest, 2 (treatment) X 2 (gender) factorial, independent group design.
Application: Happiness is operationalized by the change in scores obtained on the Satisfaction with Life Scale (SWLS). As can be seen from exact items on the Satisfaction with Life Scale, each is intending to tap into the construct "satisfaction" with life, such as the item "I am satisfied with life." and the item "In most ways my life is close to my ideal.". Operationalizing is mapping the items onto the construct.
Cozby, P. C. (2009). Methods of Behavioral Research: Tenth Edition. New York, NY: MCGraw-Hill.