What term is used to describe a characteristic of units in a study?

The term "variable" is used to describe a characteristic of units in a study because it represents any trait, quality, or attribute that can change or vary among the units being studied. In research, variables are crucial as they can take on different values and allow for analysis of relationships and effects. For example, in a study examining the impact of education level on earning potential, both education level and earning potential would be considered variables because they can differ widely among individuals.

The other terms serve different purposes in research contexts. "Factor" often refers to an explanatory variable or condition in experimental designs, typically used to denote specific influences that affect the outcome rather than the characteristic itself. "Measurement" pertains to the act of quantifying or assessing the variables, while "criterion" usually refers to a standard or principle by which something is evaluated or judged, not a characteristic of the units. Hence, "variable" is the most accurate choice for describing a characteristic of units in a study.