Most people have a large degree of variability in their heart rates during the course of a day.
It tells us little to nothing about variability by region, by education level, by type of jobs.
variable var·i·a·ble (vâr'ē-ə-bəl, vār'-)
Likely to change or vary; subject to variation; changeable.
Tending to deviate, as from a normal or recognized type; aberrant.
Having no fixed quantitative value.
Something that varies or that is prone to variation.
A quantity that is capable of assuming any of a set of values.