Final answer:
The correct term for investigating the reason for a problem or failure is a 'root cause.' The process of performing a root cause analysis involves gathering information, consulting with experts, and using problem-solving strategies to address not just the symptoms but the actual issue causing the problem. Therefore, the most appropriate option is 2.
Step-by-step explanation:
Once a problem is identified, it is important to investigate the root cause, or the reason for the problem or the failure. Root cause analysis is an analysis of a problem or situation to find the real cause of the problem and deal with it. If we do not perform a root cause analysis, we often end up dealing only with the symptoms of the problem. To effectively tackle any problem, first gathering information from customers and other stakeholders is crucial. Also, finding expert information through various means is necessary to inform the analysis. Doing a root cause analysis involves asking questions like: "What is the cause of the problem?", "What is the effect of the problem?", and "What makes this problem a problem?" This process helps to properly identify what the real problem is. Using problem-solving strategies helps to determine whether an answer is reasonable. If it is not, it further assists in identifying the cause of the discrepancy. Experts often use these strategies as a guideline and their experience to foresee the answer even before a detailed analysis, thus providing direction in the root cause investigation.