Chapter 10 dealt with selected descriptive statistics that can be used in various decision making contexts or in examining psychometric properties of scores from various assessment tools. Data on constructs we measure can be generated through four measurement scales: nominal, ordinal, interval and ratio. Variables we measure with assessment tools can be distributed in a continuous or discrete form. Before we begin data analysis, we should let the level of scaling and the variable’s distribution properties guide our decisions on analytic procedures. For achievement and attitudinal measures, we usually assume continuous, equal interval scale properties.

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