ABSTRACT
Although the measurement of variables is an often-overlooked aspect of research design, good measurement is critical to the success of a research project. In this chapter, we discuss the relevant aspects of high-quality measurement. The chapter starts with the conceptual and operational definitions of the concepts the researcher is trying to measure. It then discusses the different types and levels of measurement. The chapter then discusses the factors that should lead a researcher to choose one measure over another: reliability, operational validity, and sensitivity. Reliability evaluates the consistency of a measure and is especially important for measurement. The chapter discusses the three dimensions of reliability: stability, equivalence, and internal consistency. Throughout the chapter, we discuss methods for assessing these critical measurement factors. In addition to these measurement factors, we discuss further use of the measures and the importance of operational validity, concurrent validity, predictive validity, and the sensitivity of the measure. In practice, measurement is important because administrative and policy decisions are often based upon research, and if the measurement is poorly conceived, then incorrect decisions may be made or resources wasted on faulty research.
