ONE GOOD IDEA
Bringing the Fishbone Diagram Into the Computer Age
by William A. Levinson
The cause and effect, or fishbone, diagram is an established problem solving tool. It is particularly suitable for use by cross functional teams, helping a group organize a problem’s potential root causes in an easily understandable visual format. Despite its power and simplicity, it has practical limitations.
Many diagrams end up in computers because they’re reviewed by management or are needed to illustrate ideas in storyboards. The diagrams do not always fit neatly into a computer format—they are limited to one or two levels to maintain readability. The normal rendition is a neat but insufficient rendition of the team’s analysis on 8.5- x 11-inch paper.1
A team can rapidly run out of room on paper or marker boards—with no convenient way to save and distribute the information.
Modern computer technology, specifically the drop down file folder organization, can enhance the diagram’s power and ease of use.
Using the computer file folder directory format to organize complex information isn’t new.2 Adaptation of the fishbone diagram to this format (Figure 1) offers advantages:
- Each directory can contain an unlimited number of subdirectories. It can be expanded to display the detailed information or collapsed to hide it. Subdirectories also can hold supporting information like the results of designed ex-periments. Files can be placed right into the fishbone diagram for the team’s convenience and retained as quality records.
- It can combine the five whys, or question to the void, technique with the cause and effect diagram. An entry on the fishbone might prompt the question, “Why does this happen?” which can lead to a cascade of subfolders, each answering the preceding question and prompting another “why?” The problem’s root cause is often found when you can go no further.
Figure 2 shows how an example might be treated, with the final why identifying the problem’s root cause and a possible permanent correction.3
- Because it’s electronic, it is easy to incorporate into a quality record such as a team oriented problem solving, eight disciplines (Ford Motor Co.’s TOPS-8D) or define, measure, analyze, improve and control improvement project.
The figures were created in Microsoft Explorer, but this isn’t ideal. A newsgroup or discussion board format accessible to all team members can is more suitable for collaboration.
Trimming the Fishbone
By allowing the accumulation and display of far more information than the traditional cause and effect diagram, the nested file folder and discussion board formats offer the dangerous temptation to allow the fishbone to expand indefinitely.
A diagram with 50 or more entries is too complex and should be broken into separate pieces. Make sure the diagram addresses only one independent problem.
The quality sciences already provide for the elimination of potential causes or factors that investigation shows to be irrelevant to the problem.
At the qualitative level, the is/is not diagram from Ford’s TOPS 8D procedure eliminates potential causes that are not consistent with the problem’s description or symptoms. Application of these techniques and others allows the team to trim the fishbone by eliminating branches that, on investigation, turn out to lead nowhere.
Don’t simply delete the branches. They should be grayed out (like a nonfunctional option on a computer toolbar) or designated by a symbol when they no longer deserve attention because:
- It leaves an auditable quality record of all the work done, thus supporting ISO 9001’s closed loop corrective action requirement.
- It saves another team the effort of possibly performing the same experiments that trimmed the nonproductive branches.
The fishbone diagram is a quality record that others might use in future problem solving investigations.
- Martin Hedley, “Curse of the Super-fish-al,” Quality Progress, Vol. 38, No. 6, 2005, p. 96.
- Jeffrey Morgan, Creating Lean Corporations: Reengineering From the Bottom Up to Eliminate Waste, Productivity Press, 2005.
- Imai Massaki, Gemba Kaizen: A Comm-onsense, Low-Cost Approach to Management, McGraw-Hill, 1997.
WILLIAM A. LEVINSON is the principal of Levinson Productivity Systems, P.C,. in Wilkes-Barre, PA. He received his master’s degrees in business administration, operations research and applied statistics from Union College in Schenectady, N.Y. Levinson is an ASQ certified quality engineer, quality auditor, quality manager, reliability engineer and Six Sigma Black Belt. He is a senior member of ASQ.