Robert DeVellis demystifies measurement by relating it to familiar experiences and by emphasizing a conceptual rather than a strictly mathematical understanding. Students' attention is drawn to important concepts that are foundational for subsequent topics, with opportunities provided to test understanding through chapter summaries and exercises. The Fourth Edition includes more attention to content validity and its relationship to scale breadth; a more thorough examination of coefficient alpha's limitations and remedies; discussion of "big measurement" vs "small measurement"; and additional discussion of the bifactor model in the chapter on factor analysis.