Ishikawa Diagrams

Introduction to Ishikawa Diagrams

Also sometimes known as fishbone diagrams or herringbone diagrams Benefits: Shows the causes of an event Demonstrates where quality issues might arise Allows management to determine which issues have to be addressed in order to gain or avoid a particular event Determine which resources are required at specific times

Drawbacks: Not useful for complex problems Based on opinion not evidence Assumes problem is composed of a limited number of causes only

To successfully build a Ishikawa diagram: Everyone must agree on what the problem is Each line of causality must be pursued back to its root cause Emptier branches should be grafted onto others and overcrowded ones should be split up

Steps involved in building an Ishikawa Diagram

1. Write the problem to be solved on one side of the workspace (known as the effect), then draw the backbone of the fish 2. Decide how to categorise the causes       Manufacturing industry usually uses: Machine Method Materials Measurement Man(People) Medium (Environment)       Services industry usually uses the same categories but: Remove: Machine Method Replace with: Policies (High level decisions and rules) Procedures (Specific tasks) 3. Group potential causes into categories and sub categories       Sub categories can come from Brainstorming, calling on prior experience of team Data collected from check sheets or other sources 4. Quantify the relationship between the primary root causes and the effect Regression analysis to quantify correlation Designed experiments to quantify causation

Example of an Ishikawa Diagram