The four levels of staging a decubitus ulcer exemplify what scale of measurement?

The staging of a decubitus ulcer, which commonly categorizes the severity of pressure injuries from stage I (non-blanchable redness) to stage IV (full-thickness tissue loss), is a clear example of an ordinal scale of measurement. In an ordinal scale, the data can be organized into a ranked order based on the degree or level of the characteristic being measured.

With the stages of a decubitus ulcer, each stage represents a progression in the severity and implications of the wound. Stage I indicates early tissue damage, while Stage IV represents a much more severe condition, demanding more intensive intervention. The stages do not have equal intervals between them; for example, the difference in severity between Stage II and Stage III is not quantifiable in the same manner as an interval scale, making this incorrect for interval categorization.

Unlike a nominal scale, which merely categorizes data without any intrinsic order (such as types of fruits), or a ratio scale that has a true zero point (like weight or height), the ordinal nature of ulcer staging allows for ranking but does not entail equal spacing of values. Thus, this framework effectively reflects the progression of the condition as a ranked order of severity, aligning it with the characteristics of an ordinal scale.