Manufacturing activity involves processes which are influenced by the Material, Machine, Measurement, Method, Man and Environment. Understanding the impact of the changes on the outgoing quality is the key to process control. Controlling these variables is the experienced way of assuring quality instead of the still traditional way of 100% inspection. I have listed the hints to understand the process variables.
Checking the FTR, ETR, Downstream Rejections and Customer Complaints will reinforce the importance of process variables.
Finally, recognising that each one of us can only influence the future and not the past is a strong motivator to start with the basics to understand the process variables.