Cause and Effect -- Fishbone Diagram

Cause and Effect

Everyone has to make decisions on daily bases. Why? Because life is full of choices to make. Whether it is an important decision that requires careful thought and consideration or a quick decision, like what is for lunch. Wouldn’t it be nice to have the knowledge about a tool or technique to help you make those important decisions? No, “what’s for lunch”, is not an important decision. However, changing jobs, buying a car, planning a wedding, or running a business requires critical thought and decision-making. Having the right tool or procedure can be very beneficial and time saving when making those decisions. We are going to review the Cause and Effect Diagram, better known as the Fishbone Chart, why and when you would use this method, and examples of real experiences with this diagram.

Fishbone Chart

A Japanese quality control statistician, Dr. Kaoru Ishikawa, invented the fishbone diagram. It may be referred to as the cause and effect, fishbone, or Ishikawa diagram. It is an analysis tool that provides a way to look at effects and causes that contribute to those effects. This diagram has been used in Japan, to teach Total Quality Control, since World War II. The fishbone chart is great when dealing with a team approach to problem solving. This chart captures all the different ideas and helps create brainstorming. The fishbone helps to visualize the many potential causes for a specific problem. To construct a fishbone, start with stating the problem. Form the problem as a question, doing this will help with the brainstorming, as each person answers the question. Everyone needs to agree on the problem and then place is at the “head” of the fishbone. The remainder of the fishbone is made up of a horizontal line across the page, attached to several lines coming out vertically from this line. These branches or “bones” are labeled according to your problem. Once they have been labeled, begin the brainstorming of possible causes and attach to these branches. For each identified problem ask “why?” and attach another bone.

When to Use

Now that we have a background on how the fishbone diagram works and the inventor, we will explain when to use it in decision-making. According to North Carolina Department of Environment and Natural Resources (NCDENR) the fishbone diagram should be used “to assist teams in categorizing the many potential causes of problems or issues in an orderly way and in identifying root causes” (pp 2). Some questions to ask yourself, or team, to see if it would be beneficial to use would be: Do you need to study a problem to determine the root cause? Do you want to study all the possible reasons why a process is having difficulties or breakdowns? Do you need to identify areas for data collections? Do you want to study why a process is not performing properly or producing the desired results? If you answered, “yes” to any of these questions, it would be beneficial to your to use the fishbone diagram. While researching the fishbone diagram, I found that both NCDENR and Skymark recommend labeling the branches. The major categories include: The 4 M’s are methods, machines, materials, and manpower. The 4 P’s are place, procedures, people, and policies. The 4 S’s are surroundings, supplies, systems, and skills. (Skymark.com) These are just some examples to get you started. All of the M’s would be used in manufacturing and the P’s more in administration and service. The S’s would be used in both.

Fishbone in Use

Recently we had an uncooperative branch office. The home office was concerned about why they were not producing the results that they should be. Using the fishbone approach we laid out the problem and brainstormed with other managers on why they were uncooperative and how to get them motivated. The “head” of our fish, or the effect, was uncooperative branch. The “bones” consisted of site, task, people, equipment, and control. We knew which branch was being uncooperative, so we laid out