Final answer:
The last step of the planning process model is the implementation stage, where the selected plan is executed and may include ongoing testing and refinement.
Step-by-step explanation:
The last step of the planning process model is often associated with evaluating and refining the chosen solution or design. However, once the best alternative is selected and the implementation plan is created, the final step actually involves putting the plan into action, which could be described as the implementation stage. This involves executing the designed plan and making it work as intended, which often includes continued testing and refinement. In the context of a design process, communication of the process and results might also be considered a part of this final stage, as stakeholders and team members need to be informed about how the implementation is carried out and how the final product performs. It's important to remember that in some models, especially in public policy or project management, the planning process can be iterative, meaning that evaluation and refinement could lead back to earlier stages in the process if necessary.