Psychometric Properties
What are Psychometric Properties[edit | edit source]
Whether you identify as a student, clinician and/or researcher having confidence in your clinical tools is important.
Clinicians and researchers use clinical tools on a daily basis for evaluations, measuring change over time and establishing prognosis for patients. Our clinical reasoning can only be as strong as our tools.
Having confidence in clinical tools means that they measure what they are intended to measure (validity), they are stable over time (reliability) and can detect changes in conditions (responsiveness). Collectively, this is called looking at the psychometric properties (or methodological qualities) of a tool or outcome measure.
Psychometrics is the field of mathematics that is concerned with the statistical description of instrumental data as variables and with the inferential statistical description of the relationships between variables. (Russell 2012)
In rehabilitation medicine, psychometrics is usually concerned with measuring an individual’ physical characteristics, ability, perception of change, pain, and types of functional ability.
Psychometric properties can be applied to questionnaires, outcome measures, clinical tools, scales or special tests. For the remainder of the page, the term "tool" will apply to describe all of these categories.
Level of Measurement[edit | edit source]
Measurement instruments play an important role in research, clinical practice and health assessment (Souza, 2017).
Researchers and clinicians use measurement as a way of quantifying, understanding, evaluating and differentiating physical characteristics of the human body (Portney & Watkins 2015). This is achieved through the use of, clinical tools with patients. The nature of measurement represents quantifying (measuring) bodily characteristics; for example level of pain, range of motion, strength, or functional outcomes.
The usefulness of measurement in clinical research or practice helps with decision making and measuring progress during rehabilitation.
Validity[edit | edit source]
Validity refers to the tool's ability to measure what it is supposed to measure. Is the tool measuring the construct it is intended to? For example, does the goniometer truly measure range of motion?
Validity implies that a tool is relatively free from error. A tool that is not consistent cannot produce a meaningful measurement.
If a measurement is valid, it is always reliable. However, a measurement or tool can be reliable without being valid (consistent over time, but not measuring the construct of interest). To be classified as a tool with strong psychometric properties, it needs to be both valid and reliable (Gellman & Turner, 2013)
