Using a process or procedure that would not have achieved the intended outcome is referred to as a(n) _____.

The term that best fits the definition of using a process or procedure that would not have achieved the intended outcome is "error of planning." This term specifically relates to the initial stage of a project or process, where planning and strategy are developed. When the planning stage is flawed, the methodologies chosen may inherently lack the capacity to achieve the desired results, leading to inefficiencies or failures in execution, irrespective of how well the subsequent steps are performed.

In contrast, an execution error pertains to mistakes made during the implementation of a plan, which could stem from miscommunication, lack of training, or procedural adherence rather than the initial planning phase. Protocol deviation implies veering away from established guidelines, while system error generally refers to technical failures within a system rather than mistakes in the planning phase itself. Thus, recognizing the distinction between these concepts helps clarify why an "error of planning" is the most accurate answer when it comes to identifying the failure in the foundational stages.