Scale of measurement refers to how variables are measured. There are four different scales of measurement:
- Nominal: Classifies variables simply in terms of their names and the categories cannot be ranked. The variable “religion” with the response categories “Christian,” “Jewish,” “Muslim,” etc. is an example of a nominal scale of measurement.
- Ordinal: Contains non-numeric categories than can be ranked, such as “low,” “medium,” and “high.”
- Interval: Contains categories in which the actual distances, or intervals, between categories can be compared. For example, we can say that the difference between ages 20 and 25 is the same as the difference between ages 50 and 55.
- Ratio: Like the interval-scale variable, however it has a non-arbitrary zero value.