A cause and effect diagram is used to chart the relationship between an outcome and the factors that contribute to the outcome. Identifying the root causes or the reasons of an effect is done by using a “fishbone diagram” which was invented by Kaoru Ishikawa, according to Balanced Scorecard. Using a cause and effect diagram offers an organized format that is easy to read. Also, it identifies areas in need of additional data and indicates variations in a process and the cause.
Define the effect by identifying and stating the outcome. Use a phrase for your effect that states whether the outcome is positive or negative. Place it in a box to the far right and start your diagram.
Draw a horizontal arrow pointing to the box stating the effect. The arrow should start at the left of the page and continue right.
Identify the main categories that determine the possible causes. Use either the 3Ms and P (materials, methods, machinery and people) or the 4Ps (procedures, people, policy and plant) when possible, with environment as a fifth category if necessary. Write the categories over the line to the left of the effect box and draw a box around each category.
Create sub branches of the categories that represent the factors or causes. Place as many as possible along the line from the category box to the arrow. Use both sides of the arrow to hold the causes.
Place additional detail levels along the sub branches of he categories. Extend the arrows outward, adding detail as needed. Analyze your cause and effect diagram to determine the causes that need focus and circle them.