Fishbone diagram (C & E Diagram) is a pictorial representation of different potential causes that may be the cause of a given problem. A fishbone diagram helps the team brainstorm and list all potential causes for a given problem and capture the team's perception of the most important causes.
This tool can be added to your active workbook by clicking on Project and then selecting Cause and Effect > C&E Diagram.
Click on the Analysis Setup button on the main menu or the task menu bar to open the menu options for this tool.
A sample screenshot of the setup menu is shown below.
Enter a problem statement. The problem statement should be a brief one-line description of the problem for which you are creating the fishbone diagram. This information is entered at the head of the fish.
Specify the major categories for the fishbone diagram. The available options are:
This will use the categories: Person, Material, Method, Equipment, Measurement, and Environment. This is the default option.
This will use the categories: Product, Price, Positioning, Place, Promotion, and People
This will use the categories: Surroundings, Suppliers, Systems, Skills, and Safety
You can specify your own categories in the textboxes.
You can edit any of the text in the categories textboxes depending on your specific project needs.
Click on the tabs to move between different pages. The first tab is the problem tab which describes the problem and the major categories. Depending on the categories you specify here, the titles for the remaining tabs will change.
Click on this button to open the example file. You can view the example to get an idea of how to fill out this tool or you can use the example as a starting point and modify it to meet your project needs.
Click on this button to view the help file for this topic.
Click on this button to discard any changes and close this dialog box.
Click on this button to save changes and compute the analysis results. The system will try to equispace the causes and add them to your fishbone diagram. If you want to delete a cause, just enter a blank description for the cause and this cause will be deleted from the worksheet.
For each of the categories, click on the tab for the appropriate category and specify the causes for that category. A sample screenshot of the dialog box is shown in the figure below.
Once you select the major categories, the next step is to identify the causes within each major category. You can identify the causes either using brainstorming exercises with your cross-functional team members or use other tools such as process maps, fault tree analysis, FMEA, etc. to identify the potential causes. List all the causes for each category here.
If the cause you have identified is a potential cause for the problem statement you are working on, select the first radio button.
Most Likely Cause: If the cause you have identified is a most likely cause for the problem statement you are working on, select the second radio button. This decision is based on your brainstorming with your team members and may or may not be true, but it is the best guess estimate that it is a most likely cause from your team members. Select this radio button for the most important causes.
If the cause you have identified is an uncontrollable cause for the problem statement you are working on, select the third radio button. A cause is marked as uncontrollable if this cause is not within the span of control of your team, or it is too expensive, time-consuming, or difficult to control this cause. Make sure you do sufficient investigation to mark a cause as non-controllable. Maybe there is something you or your team could do to address this cause. All causes marked as uncontrollable will be eliminated from further analysis.
When the tool is opened, the main menu at the top may change to a task-specific menu as shown below. If this menu does not open, click on the F4 button or the small arrow at the bottom right portion of your menu group to open this menu bar.
To add a potential cause to the worksheet, you can click on the type of symbol you want to add to the worksheet and then click on the worksheet to specify the location where the symbol should be added. The software will connect the symbol to the closest major category. If the software does not connect the potential cause to the right category, then you can manually detach and attach the potential cause to a different category. The following symbols can be selected:
Potential Cause - Used to add a potential cause. This is the normal potential cause that the team members feel has an impact on the problem statement. Note, that for this diagram, it is still the potential cause and the cause has not yet been validated by data. Hence, the cause may or may not have an impact on the problem statement, but the team feels that this cause may potentially have an impact on the problem.
Uncontrollable Cause - Used to add an uncontrollable cause to the C&E diagram. Note that a cause is uncontrollable if the team does not have the resources to address this cause or the cause is too expensive or too difficult to address. Any items marked as an uncontrollable cause will probably not be carried forward, so make sure that you mark a cause as uncontrollable that is really beyond the scope of your team.
Likely Cause - Used to add the most likely cause to the C&E diagram. This is the cause that your team believes is the most likely cause of the problem that you are addressing. Of course, this is still based on the perception of the team members and needs to be validated using facts and data.
Click on Compute Outputs to update the output calculations. This will list the total number of causes identified in the Conclusion box. A sample screenshot of the worksheet is shown below.
No analysis is performed on this worksheet except to list the total number of potential causes identified, the number of most likely causes identified by the team (if any), and the number of uncontrollable causes identified by the team (if any). The more the number of potential causes your team has identified, the better.
Here are a few pointers regarding this analysis:
Since this is a standard Excel chart, you can use Excel's Insert Shapes to add other shapes to this picture if required.
Currently, Sigma Magic can only be used to create level 1 causes. All causes are attached to the main categories. If you have further levels of breakdown (by using the 5 why analysis), you can choose to add to the bottom-most level of causes to your fishbone diagram.
Do not manually add the causes & arrows since the software uses a specific naming convention for the item. You can add new causes or edit existing causes using the Analysis Setup options or by clicking on the causes on the task menu bar.
You can add any number of causes to the worksheet but the dialog box editor can only display 10 causes for each branch.
Following examples can be found in the Examples folder within the software.
Create a cause & effect (fishbone) diagram for lack of sales within a company. Brainstorm the various causes within your team and create the C&E diagram (Fishbone 1.xlsm)