The Scales Of Measurement, Ordinal Scale, Interval And Ratio

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In this write up, the different scales of measurement, nominal scale, ordinal scale, interval and ratio are discussed, including examples of test types that would usually employ them. Also, measures of central tendency, and measures of variability and their effect on test suitability are addressed in the second half of this piece. The Four Scales of Measurement Scales of measurement defines a framework wherein numbers are assigned to objects based on a set of rules (Thorndike & Thorndike-Christ, 2009). These authors presented four different types of scales of measurement as ordinal, nominal, ratio and interval. Nominal Scale Thorndike Thorndike-Christ (2009) described a nominal scale as a measurement type wherein each “number takes on the meaning of a verbal label” (p. 27). For example, in an assessment of students on a campus, girls could be labeled number 1, and the girls, number 2. In this case, the values are mutually exclusive, and the labels have no numerical significance. Assessment that would use a nominal scale could be practically any measure that affixes labels to constructs for assessments. For example, the Interprofessional Competency Model for Healthcare Leadership is an assessment model that measures constructs developed into competency models, such as analytical thinking, community orientation, financial skills, and initiative (Calhoun, Dollett, Sinioris, Wainio, Butler, Griffith, & Warden, 2008). Ordinal Scale Next, an ordinal scale describes “the order

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