Variables, a Short Taxonomy
A phenomenon that changes over time, space, objects, or living things is called a variable. If a variable’s changes could be measured, that is, expressed by numbers or quantities, then we have a quantitative variable; otherwise, we have a qualitative variable. Blood pressure is an example of a quantitative variable—because it takes different values from individual (living thing) to individual. It can be measured, and has its own scale of measurement.