Cause-and-Effect Diagram Overview
Use the Diagram platform to construct cause-and-effect diagrams, also known as Ishikawa charts or fishbone charts. Use these diagrams to:
• Organize the causes of an effect (sources of a problem)
• Brainstorm
• Identify variables in preparation for further experimentation
Example of a Cause-and-Effect Diagram
You have data about defects in a circuit board. You want to examine the major factors and possible causes of the defects in a diagram.
1. Select Help > Sample Data Library and open Ishikawa.jmp.
2. Select Analyze > Quality and Process > Diagram.
3. Select Parent and click X, Parent.
4. Select Child and click Y, Child.
5. Click OK.
Figure 13.2 Ishikawa.jmp Diagram
The major factors are Inspection, Solder process, Raw card, Components, and Component insertion. From each major factor, possible causes branch off, such as Inspection, Measurement, and Test coverage for the Inspection factor.
You can focus on one area at a time to further examine the possible causes or sources of variation for each major factor.
Prepare the Data
Before you produce the diagram, begin with your data in two columns of a data table.
Figure 13.3 Example of the Ishikawa.jmp Data Table
Notice that the Parent value Defects in circuit board (the effect) has five major factors, listed in the Child column. One of these major factors is Inspection, which has its own causes listed in the Child column. Parent values have children, and children can have their own children (and therefore be listed in both the Parent and Child columns.)
Launch the Diagram Platform
Launch the Diagram platform by selecting Analyze > Quality And Process > Diagram.
Figure 13.4 The Diagram Launch Window
Tip: To create a basic diagram that is not based on a data table, leave the Y, Child, and X, Parent fields empty and click OK. Then edit the nodes using the options in the right-click menu. See “Right-Click Menus”.
Y, Child
Represents the child factors contributing to the parent factors.
X, Parent
Represents the parent factors (including the effect) that have child factors.
Label
Includes the text from the Label columns in the nodes of the diagram.
By
Produces separate diagrams for each value of the By variable.
The Cause-and-Effect Diagram
Figure 13.5 Cause-and-Effect Diagram
In Figure 13.5, the effect or problem, Defects in circuit board, appears on the right as the center line. The major contributing factors appear at the end of the branches (Inspection, Solder process, Raw Card, and so on.) Possible causes branch off each major factor.
Right-Click Menus
Right-click on a highlighted node to modify text, insert new nodes, change the diagram type, and more. Note the following:
• Right-click on a title to change the font and color, positioning, visibility, or formatting.
• Click and highlight a node to rename it.
• Click and drag a node to move it.
Text Menu
The Text menu contains the following options:
Font
Select the font of the text or numeric characters.
Color
Select the color of the text or numeric characters.
Rotate Left, Rotate Right, Horizontal
Rotates the text or numbers to be horizontal, 90 degrees left, or 90 degrees right.
Insert Menu
Use the Insert menu to insert items onto existing nodes. The Insert menu contains the following options:
Before
Inserts a new node to the right of the highlighted node. For example, Figure 13.6 inserts Child 1.5 before Child 2.
Figure 13.6 Insert Before
After
Inserts a new node to the left of the highlighted node. For example, Figure 13.7 inserts Child 3 after Child 2.
Figure 13.7 Insert After
Above
Inserts a new node at a level above the current node. For example, Figure 13.8 inserts Grandparent at a level above Parent.
Figure 13.8 Insert Above
Below
Inserts a new node at a level below the current node. For example, Figure 13.9 inserts Grandchild at a level below Child 2.
Figure 13.9 Insert Below
Move Menu
Use the Move menu to move nodes or branches. The Move menu contains the following options:
First
Moves the highlighted node to the first position under its parent.
Last
Moves the highlighted node to the last position under its parent.
Other Side
Moves the highlighted node to the opposite side of its parent line.
Force Left
Makes all horizontally drawn elements appear to the left of their parent.
Force Right
Makes all horizontally drawn elements appear to the right of their parent.
Force Up
Makes all vertically drawn elements appear above their parent.
Force Down
Makes all vertically drawn elements appear below their parent.
Force Alternate
Draws children on alternate sides of the parent line.
Figure 13.10 Force Options
Other Menu Options
The right-click menu for a highlighted node also contains these options:
Change Type
Changes the entire chart type to Fishbone, Hierarchy, or Nested.
Uneditable
Disables all other commands except Move and Change Type.
Text Wrap Width
Specifies the width of labels where text wrapping occurs.
Make Into Data Table
Converts the currently highlighted node into a data table. Convert the all nodes by highlighting the whole diagram (effect).
Close
Shows the highlighted node.
Delete
Deletes the highlighted node and all of its children.
Save the Diagram
There are different ways to save your diagram. Choose from one of the following:
• save the diagram as a data table
• save the diagram as a journal
• save the diagram as a script
Save the Diagram as a Data Table
1. Highlight the entire diagram.
2. Right-click and select Make Into Data Table.
3. Save the new data table.
Note the following about this approach:
• If you have other processes that need to update the data table, this can be a good approach to choose.
• Very little customization is available, because the data table cannot represent the customization.
Save the Diagram as a Journal
1. Highlight the entire diagram.
2. Right-click and select Edit > Journal.
3. Save the new journal.
Note the following about this approach:
• This option can be a good choice for impromptu work. For example, you can manually build the diagram, save it as a journal, then reopen the journal later and continue building and editing the diagram.
• Any customization exists only in the journal, and the journal is not connected to the data table.
Save the Diagram as a Script
1. From the red triangle menu, select Save Script > To Script Window.
2. Save the new script.
Note the following about this approach:
• If you have other processes that need to update the data table, this can be a good approach to choose.
• If you created the diagram from a data table, a simple script appears that relaunches against the data table with no customization.
• If you created the diagram without using a data table (or from a journal), a more complex script appears that contains all the commands needed to add and customize each area of the diagram.
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