Fault Tree Analysis Diagrams

"Root cause analysis (RCA) is a method of problem solving that tries to identify the root causes of faults or problems. ...
RCA (in steps 3, 4 and 5) forms the most critical part of successful corrective action, because it directs the corrective action at the true root cause of the problem. Knowing the root cause is secondary to the goal of prevention, but without knowing the root cause, it is not possible to determine what an effective corrective action for the defined problem would be. ...
3. Ask "why" and identify the causes associated with each step in the sequence towards the defined problem or event. "Why" is taken to mean "What were the factors that directly resulted in the effect?"
4. Classify causes into causal factors that relate to an event in the sequence and root causes, that if eliminated, can be agreed to have interrupted that step of the sequence chain.
5. Identify all other harmful factors that have equal or better claim to be called "root causes." If there are multiple root causes, which is often the case, reveal those clearly for later optimum selection." [Root cause analysis. Wikipedia]
This root cause analysis (RCA) tree diagram example "Sale problem solution" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Seven Management and Planning Tools solution from the Management area of ConceptDraw Solution Park.