Tag Archives: fishbone diagram

All About Fishbone Diagrams

An Ishikawa or fishbone diagram is a visualization tool for categorizing the potential causes of a problem in order to identify its root causes. These diagrams are particularly useful in brainstorming sessions as they help people to focus their conversation.

The technique is named after Dr. Kaoru Ishikawa, a Japanese quality control expert, who invented it to help employees avoid solutions that merely address the symptoms of a much larger problem. The approach begins by stating the problem, and then requires people to identify at least four overall causes or categories that contributed to the problem. Once categories are selected, the team must brainstorm around each cause to further break-down how or why the effect took place.

Because the design of the diagram looks much like a skeleton of a fish, it is commonly referred to as a fishbone diagram.

Common uses of the fishbone diagram range from product design and quality defect prevention to identifying potential factors causing an overall effect or process failure. Each factor or cause for imperfection is a source of variation.

After brainstorming all the possible causes for a problem, users go on to rate the potential causes according to their level of importance and diagram a hierarchy.

Simple Implementation

Fishbone diagrams are typically worked right to left, with each large “bone” of the fish branching out to include smaller bones containing more detail.

  • Create a head, which lists the problem or issue to be studied.
  • Create a backbone for the fish (straight line which leads to the head).
  • Identify at least four “causes” or categories that contribute to the problem. Major categories often include: equipment or supply factors, environmental factors, rules/policy/procedure factors, and people/staff factors. Connect these four causes with arrows to the spine. These will create the first bones of the fish.
  • Brainstorm around each “cause” to document those things that contributed to the cause. Use the 5 Whys or another questioning process such as the 4P’s (Policies, Procedures, People and Plant) to keep the conversation focused.
  • Continue breaking down each cause until the root causes have been identified.

Continuous Improvement & Key Charting Tools

In an earlier post we shared thoughts on “Ten Continuous Improvement Tools,” each of which designed to help people  examine current reality from a different angle.

Included in the list are several key charting tools, which are particularly useful for sifting through potentially large quantities of data and translating the data into more useful information. These tools also make the work more “visible,” and give those involved in studying the work a common language.

Here is a list of five key charting tools:

  1. paretoPareto: simple bar chart that ranks and displays data in descending order, and that helps us decide what to work on — the “vital few” vs. the “less important many.”  Often referenced as the 80/20 principle.
  2. runchartRun:  A run chart is a graph that displays data points of some characteristic being measured as they occur over time. It is used to visually display process performance over time and to identify meaningful trends or shifts in the average, thus telling us  “how things are going” and prompting us on what to investigate further.
  3. flowchartFlow: A flow chart is a simple diagram of the steps in a process. It is used to identify actual or ideal paths that a process follows, and shows basic steps and decision points, recycle loops, work and wait times, and can highlight problems or opportunities for improvement
  4. histogramHistogram: A column chart showing the distribution of values by frequency. It is a set of data with a range of measurements. The height of a bar corresponds to the relative frequency of the amount of data in the class.
  5. fishboneFishbone: A charting technique used for identifying all of the possible causes of particular “effect” or problem… for linking conditions for results. A fishbone chart can help us identify root causes of problems by asking the simple question,  “why?”  multiple times.