The text explains that quality control directives are crucial for analysis but not enough to ensure statistical control, which is managed by quality assessment???a key part of quality assurance. Quali...The text explains that quality control directives are crucial for analysis but not enough to ensure statistical control, which is managed by quality assessment???a key part of quality assurance. Quality assessment helps maintain, detect, and suggest solutions for loss of statistical control. It includes internal methods, like analyzing duplicate samples and spikes, and external methods, such as laboratory certification by an agency.