The individual variation may be caused by many factors, such as genetics, environment, disease stage and diet, etc, among which genetic polymorphism is a common and uncontrollable factor.

There's another factor that prevents people from being model financial citizens (besides, of course, uncontrollable circumstances like joblessness).

Temperature is an important factor which affected the precision of the electrical instruments. Acute change of temperature had an uncontrollable effect on the circuit.