Measurement

In Psychometric Theory, Jum Nunnally and Ira Bernstein define measurement, in part, as a set of rules to represent the standing of an individual or collection of individuals (e.g., pair, group, culture, society) relative to a domain of interest. In human lifespan development research, these rules can take the form of numerical quantities, qualitative levels (e.g., low vs. high), nominal categories (e.g., male vs. female), or any combination of the three. For example, a researcher may administer a numerically based instrument to measure a child’s weight and height (e.g., scale) and then, based numerical estimates of the child’s weight and height, assign the child a number (e.g., body mass index). This number can be compared to the numbers of other children to derive a categorical ...