(1) preliminary control of input which is a preventive and proactive control, addressing the system of causes such as equipment, training and raw materials;
(2) concurrent control is done on a real-time basis to make sure that work is performed according to design procedures;
(3) rework control is performed at the output level, where defective items are reworked; and
(4) damage control is performed to minimize the negative impact on customers who receive defective products or services. This can be done through apologizing, replacing the product or service, and refunding.