What are the advantages and limitations of fishbone diagrams compared to other root cause analysis tools?

O Diagrama Espinha de Peixe, ou Diagrama de Ishikawa, ou 6M, ou Análise de Causa e Efeito (meu nome preferido por representar de forma mais clara o seu propósito) é uma forma de correlacionar o efeito, o qual está descrito na "cabeça do peixe" com suas possíveis causas, divididas nos 6Ms (mão de obra, método, máquina, material, meio ambiente e medição). O efeito fica do lado direito do Diagrama e está ligado com uma linha central perpendicular aos 6Ms que são expostos três acima e três abaixo desta linha em linhas diagonais. Desta forma, fica parecido com um peixe, por isso o nome. Após as correlações serem feitas através de brainstorming, é importante ir para o Gemba para confirmar ou descartar cada uma das hipóteses levantadas.

A fishbone diagram is a powerful tool we use to help businesses figure out the root causes of their problems. This diagram lays out all the clues (causes) that could lead to the issue (effect). This also helps the teams to brainstorm and dig deeper into what's really going on, making problem-solving a more collaborative and thorough adventure.

Fishbone diagrams, or Ishikawa diagrams, excel in visually organizing potential causes for a problem, fostering team collaboration. They're intuitive and identify root causes comprehensively. However, their subjective nature can lead to interpretation bias. In comparison to tools like the 5 Whys, fishbone diagrams offer a broader perspective but may lack the depth of detailed probing. They shine in group discussions but might not provide as straightforward a path to a singular root cause. Balancing breadth and depth, fishbone diagrams suit complex issues requiring diverse input but may benefit from supplementary analysis tools.

A principal vantagem do Diagrama de Espinha de Peixe (e das demais ferramentas de análise) é fazer com que o pensamento seja estruturado e direcionado. Neste caso o direcionamento se dá através dos 6Ms (mão de obra, método, máquina, matéria prima, medição e meio ambiente), o que facilita o entendimento e a percepção de relação causa e efeito existentes entre a cabeça do peixe (onde deve ser descrito o problema / fenômeno) e as espinhas do peixe onde estão listados os 6Ms.

Promotes analytical thinking and problem-solving skills among team members. Provides a visual representation of problems, making it easier to communicate issues and solutions across teams and departments.

It can be time-intensive to create and refine, especially for complex issues with many potential causes. The effective use may require expertise or experience to guide the process and ensure meaningful outcomes. It focuses on identifying causes rather than offering direct solutions, requiring further steps for problem resolution.

A limitação está em dois pontos na minha opinião. O primeiro é que ele não chega na causa raiz, sendo necessário usar o 5 Porquês para dar continuidade na análise. Um segundo ponto que entendo ser uma limitação é que os 6Ms são muito bem aplicados e adequados para processos industriais, porém quando vamos para serviços, saúde, distribuição, varejo, a lógica apresenta algumas dificuldades para ser colocada em prática. Uma terceira limitação seria a espinha de peixe virar espinha de baleia, mas como citado nos passos anteriores quanto a verificação no Gemba, isso sendo bem feito este problema não deverá acontecer.

The fishbone is a valid exercise, but on a daily basis it can be superficial and/or biased, leaving important points out. A good root cause analysis needs a critical look, in this sense the 5G, 5W2H and 5Why’s techniques seem to me to get to the right point faster.

In my experience, fishbone diagrams done in team meetings helps to identify a list of causal factors. The team gets a grasp of the problem - both the breadth and depth of the issue. The next step after prioritizing the causal factors, is to use an RCA technique, 5-Why or TapRoot work great, to dig into the the high-priority causal factors. The goal is for the team to get to "the root" of the problem. From the RCA, the team can easily identify solutions. Then the hard part: Getting resources to implementing solutions and actually putting them into place.

When figuring out why a problem happened, think about if the problem is simple or complex. For easy problems, just asking "why?" several times (the 5 Whys) might work. For harder ones, drawing a Fishbone Diagram can help see many possible reasons. Then, using Pareto Charts can show which reasons are the biggest deal by seeing which ones happen the most. The idea is to first find out what the biggest parts of the problem are and then understand why they're happening, in a step-by-step way. This helps to focus on what really matters and fix it properly.

Fishbone diagrams offer a visual representation that helps identify potential root causes systematically. Their advantages include simplicity, accessibility, and facilitation of brainstorming sessions. However, they may oversimplify complex issues and lack quantitative analysis. Contrarily, tools like the 5 Whys delve deeper into causality but may miss interconnected factors. Fault tree analysis provides a structured approach but can be time-consuming. Each method has strengths and weaknesses; choosing the right one depends on the complexity of the problem and the depth of analysis needed.