Conditions for experimental evaluation
System being observable: To transform quality to quantity:
System being stable:The system must be able to remain at some determined status under constant experimental conditions.
System being controllable :The system output (dependent variables) must be sensitive to the change of input (independent variables).
(The selected dependent variables and independent variables must have an observable cause-effect relationship. )
You must have a goal for an experiment, e.g, to test some predefined hypotheses, to gain more information about problem space, to identify variables in relation to a problem under investigation.