Terminology 101: Introduction to psychometric measurement
Psychometric measurement: A field of research that focuses on the development and validation of assessment tools to measure abstract variables
Nurse researchers conduct research on a wide range of concrete and abstract variables, which they need to properly measureto generate meaningful results. To properly measure variables, researchers must quantify (assign numeric scores to) their observations while ensuring that the numeric scores they obtain accurately reflect the variables they intend to measure. Concrete variables such as one’s height or waist circumference are tangible in nature and thus can be directly measured (using a tape measure in this example). In contrast, variables representing abstract concepts such as one’s quality of life, job satisfaction or depression are intangible in nature and thus cannot be directly measured.
How can we meaningfully and accurately quantify abstract variables? The field of research that answers this question is known as psychometrics. In psychometric research, investigators use their knowledge of how the concept they intend to measure manifests itself to create a measurement tool that captures the way in which, or the degree to which, an individual experiences this concept. Psychometric tools are commonly referred to as inventories, instruments, questionnaires, measures, surveys or scales.
To develop a psychometric measure of an abstract variable, researchers start by identifying proxy indicators for the variable. Think of these proxy indicators as the manifestations of the concept in an individual. For example, sleeplessness, loss of appetite and feeling disliked are documented proxy indicators of depression. Researchers then create questions or statements, often called items, that will enable them to collect information from their research participants about the proxy indicators and thereby quantify the abstract variable of interest. The list of items is presented to study participants in the form of a single psychometric measure. Often, individuals are asked to respond to the items of a psychometric measure using a Likert scale, with scores commonly ranging between 1 (for “strongly disagree,” for instance) and 5 (for “strongly agree,” for instance). For the simplest types of psychometric measures, a research participant’s overall score for the variable that the psychometric measure was designed to quantify is calculated by adding the participant’s response scores on all of the items of the tool.
The central question pertaining to the use of psychometric measures is this: how does one know that a measure does indeed properly quantify the abstract variable of interest? For instance, how do researchers using the Center for Epidemiologic Studies Depression Scale know that it is a good measure of depression and that it doesn’t measure something else? The answer to this question will be the focus of the next two columns in this series. They will address the principles of validity and reliability, two indices that provide evidence that a psychometric measure is both appropriate and accurate.
Nurse.ONE.ca resource on this topic
- Fain, J. A. (2013). Reading, Understanding, and Applying Nursing Research (4th ed.).