General speaking, Human Factors explores a problem by looking at the humans within a system, their interactions with each other and the system and then re-designing the tasks, interfaces and system; it uses a combination of systems analysis approaches and design-thinking where humans are the components of the system.
QI generally looks at the system to define processes and implement changes for improvement based on testing different approaches to achieve the desired outcome. The processes are mostly delivered by people, but the people are not the focus. It uses systems analysis where processes are the components of the system.
Bringing both together offers significant synergistic approaches and benefits.
