Final answer:
Quality standards are primarily refined during the design phase after initial testing reveals ways to improve the design to better meet quality criteria and constraints. The correct option is 3) design phase
Step-by-step explanation:
Quality standards are refined during various phases of the design process, which include conceptualization, planning, design, and implementation. However, when specifically considering refinement, this typically occurs after initial testing and evaluations. Refinement is where a design is iterated upon to better meet the criteria and constraints set forth for the project. It is a step that falls under the broader 'design phase' where the selected concept is detailed, prototyped, and tested extensively. Through this testing, weaknesses may be found, leading to further refinement.
During the 'implementation phase', the focus shifts to manufacturing the product or constructing the design. Although adjustments can still be made if new challenges arise, this phase is more about bringing the refined design to fruition. Refinement of quality standards is an iterative process requiring flexibility and an ability to adapt to new findings, which predominantly falls within the design phase - when most of the iterative prototyping and testing happens.
The process of refining the design may lead back to earlier stages if the design does not work as intended, demonstrating the non-linear nature of design refinement within the design process. The correct option is 3) design phase