"Quality assessment"

is the data collection and analysis through which the degree of conformity to predetermined standards and criteria are exemplified. If the quality, through this process is found to be unsatisfactory, attempts are made to discover the reason for this.

"Quality assurance"

is a way of preventing mistakes and defects in manufactured products and avoiding problems when delivering products or services to customers; which ISO 9000 defines as "part of quality management focused on providing confidence that quality requirements will be fulfilled.

"Quality of performance"

is how well the product functions or service performs when put to use. It measures the degree to which the product or Service satisfies the customer from the perspective of both quality of design and the quality of conformance.