A diagram is a symbolic representation of information according to some visualization technique. Diagrams have been used since ancient times, but became more prevalent during the Enlightenment.

The affinity diagram
It is business tool used to organize ideas and data. It is one of the Seven Management and Planning Tools. People have been grouping data into groups based on natural relationships for thousands of years; however, the term affinity diagram was devised by Jiro Kawakita in the 1960s[1] and is sometimes referred to as the
KJ Method.

The tool is commonly used within project management and allows large numbers of ideas stemming from brainstorming[2] to be sorted into groups, based on their natural relationships, for review and analysis.[3] It is also frequently used in contextual inquiry as a way to organize notes and insights from field interviews. It can also be used for organizing other freeform comments, such as open-ended survey responses, support call logs, or other qualitative data.

The affinity diagram organizes ideas with following steps:

• Record each idea on cards or notes.
• Look for ideas that seem to be related.
• Sort cards into groups until all cards have been used.

Once the cards have been sorted into groups the team may sort large clusters into subgroups for easier management and analysis.[4] Once completed, the affinity diagram may be used to create a cause and effect diagram.[5]

In many cases, the best results tend to be achieved when the activity is completed by a cross-functional team, including key stakeholders. The process requires becoming deeply immersed in the data, which has benefits beyond the tangible deliverables.

Fishbone diagram

Looking for more quality tools?

Fishbone Diagram

5 Whys

QToolsTM Bundle

Plan-Do-Study-Act plus QToolsTM

Also Called: Cause–and–Effect Diagram, Ishikawa Diagram

The fishbone diagram identifies many possible causes for an effect or problem. It can be used to structure a brainstorming session. It immediately sorts ideas into useful categories.

When to Use a Fishbone Diagram

When identifying possible causes for a problem.

Especially when a team’s thinking tends to fall into roots.

Fishbone Diagram Procedure

Materials needed: flipchart or whiteboard, marking pens.

Agree on a problem statement (effect). Write it at the center right of the flipchart or whiteboard. Draw a box around it and draw a horizontal arrow running to it.

Brainstorm the major categories of causes of the problem. If this is difficult use generic headings:

• Methods
• Machines (equipment)
• People (manpower)
• Materials
• Measurement
• Environment

Write the categories of causes as branches from the main arrow.

Brainstorm all the possible causes of the problem. Ask: “Why does this happen?” As each idea is given, the facilitator writes it as a branch from the appropriate category. Causes can be written in several places if they relate to several categories.

Again ask “why does this happen?” about each cause. Write sub–causes branching off the causes. Continue to ask “Why?” and generate deeper levels of causes. Layers of branches indicate causal relationships.

When the group runs out of ideas, focus attention to places on the chart where ideas are few.

Tree Diagram

Also called: systematic diagram, tree analysis, analytical tree, hierarchy diagram

The tree diagram starts with one item that branches into two or more, each of which branch into two or more, and so on. It looks like a tree, with trunk and multiple branches.

It is used to break down broad categories into finer and finer levels of detail. Developing the tree diagram helps you move your thinking step by step from generalities to specifics.

When to Use a Tree Diagram?

When an issue is known or being addressed in broad generalities and you must move to specific details, such as when developing logical steps to achieve an objective.

When developing actions to carry out a solution or other plan.

When analyzing processes in detail.

When probing for the root cause of a problem.

When evaluating implementation issues for several potential solutions.

After an affinity diagram or relations diagram has uncovered key issues.

As a communication tool, to explain details to others.

Tree Diagram Procedure

Develop a statement of the goal, project, plan, problem or whatever is being studied. Write it at the top (for a vertical tree) or far left (for a horizontal tree) of your work surface.

Ask a question that will lead you to the next level of detail. For example:

For a goal, action plan or work breakdown structure: “What tasks must be done to accomplish this?” or “How can this be accomplished?”

For root–cause analysis: “What causes this?” or “Why does this happen?”

For gozinto chart: “What are the components?” (Gozinto literally comes from the phrase “What goes into it?”

Brainstorm all possible answers. If an affinity diagram or relationship diagram has been done previously, ideas may be taken from there. Write each idea in a line below (for a vertical tree) or to the right of (for a horizontal tree) the first statement. Show links between the tiers with arrows.

Do a “necessary and sufficient” check. Are all the items at this level necessary for the one on the level above? If all the items at this level were present or accomplished, would they be sufficient for the one on the level above?

Each of the new idea statements now becomes the subject: a goal, objective or problem statement. For each one, ask the question again to uncover the next level of detail. Create another tier of statements and show the relationships to the previous tier of ideas with arrows. Do a “necessary and sufficient check” for each set of items.

Continue to turn each new idea into a subject statement and ask the question. Do not stop until you reach fundamental elements: specific actions that can be carried out, components that are not divisible, root causes.