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Interrelationship Diagram is a pictorial tool that helps in visualizing the cause and effect relations among multiple items, factors or problems. The items are connected by lines, where the head of the arrow depicts an Effect while the tail of the arrow depicts a Driver. The item with the maximum tails gets identified as the principle cause.


An application-oriented question on the topic along with responses can be seen below. The best answer was provided by Joyal and Sourabh Nandi.


Applause for all the respondents - Aritra Das Gupta, Joyal, Sourabh Nandi, Twinkle Patnaik, Natwar Lal.


Also review the answer provided by Mr Venugopal R, Benchmark Six Sigma's in-house expert.


Q 297. Interrelationship diagram help discover, visualize, and communicate high-level sequential or cause-and-effect relationships. Clustering and sequencing of causes are the main steps involved in the construction of an interrelationship diagram. In what scenarios would do you find the use of the tool relevant?



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An interrelationship diagram can  depict relationship in a complex situation; the one which are not easily traceable.

It can be best used when 

1. Trying to understand links between ideas or cause and effect relationships; especially when trying to identify greatest impact of improvement 

2. When complex issue is analyzed for causes

3. When complex solution is being implemented 

4. In RCA, to understand how different aspects of problems are connected 

Seeing that relationship between problem and possible cause can be further analyzed 

5. After generating fish bone and tree diagram,  to more completely explore relations of ideas

Practical examples:-

1. A computer support group planning to replace mainframe computers; the interrelationship diagram can be drawn to sort out a confusing set of elements involved in project. The ideas that were brainstormed were a mixture of action steps, problem, desired results and less desirable effects handled. All these ideas went onto diagram together.

2.Decline in productivity at a workplace,  as resources hired is a cost to the company.


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Benchmark Six Sigma Expert View by Venugopal R

Union of Japanese Scientists and Engineers (JUSE) came out with ‘New Seven QC tools’ in the late 1970s; and Interrelationship Diagram was included as one of them. These tools were also called as ‘Management & Planning’ tools.


While dealing with multiple factors that are believed to be impacting a problem, the Interrelationship diagram serves as a useful tool to pictorially represent the 'Cause & Effect' relationships among all the factors and also help to visualize the relative extent of impact of the factors towards the ultimate ‘effect’, to a great extent.


A simple example will help to understand this tool quickly.


An organization wanted to study why they were not getting the desired level of improvement in sales after subjecting their staff to ‘Learning and Development’ program for imparting the skills to improve sales. The relevant stakeholders did a brainstorming and came up with the following possible causes:

  1. Insufficient training duration
  2. Trainer caliber
  3. Inadequate practical training
  4. Poor training plan
  5. Qualifying exam too easy
  6. Candidate background
  7. Insufficient training content
  8. Low skill imparted


For the above example, a interrelationship diagram was constructed as below for the identified factors



The arrows connecting the factors represent the ‘Cause and Effect’ relationship. For instance, “Poor Training Plan” has 5 outgoing arrows. The factor where an arrow begins is the cause whose effect is the factor where the arrow ends. Thus “Insufficient content” is the effect for the cause “Poor training plan”.


For each factor, the number of incoming and outgoing arrows are mentioned beside the respective boxes. It may be noticed that there are factors for which there is no incoming arrow, but only outgoing arrows. Such factors represent only a 'cause' and are not the 'effect' of any other factor (E.g.: Poor Training Plan).


We may also have factors with only incoming arrows and no outgoing arrows. Such factors are the 'effect 'of many other factors and are not 'cause' for any of the other factors. (E.g.: Low skill imparted).


It could be seen that the interrelationship diagram provides a visual picture of not only the C&E relationships among the factors but also an extent of prioritization of the causes that have higher influence upon the final effect.


Where would we find this tool relevant and useful?

  1. During a Lean Six Sigma Project, after brainstorming, once the primary causes are identified and we need to shortlist the prioritized causes, this tool will be handy.
  2. Similarly, during the solution identification for a problem, once we list out the possible solutions, an interrelationship diagram can provide clarity on the solutions that result in the best effect.
  3. Even for identifying a set of projects to work on, this tool will help us to narrow down from a list of projects, to remove most of the redundancy, based on the interrelationships.
  4. Whenever we use affinity diagrams, fish bone diagrams or tree diagrams, we can use the Interrelationship diagram to explore their relationships.
  5. When we have to work with a set of factors (causes) that are overlapping and related, the Interrelationship diagram helps to clear up the clutter and help us to proceed with more clarity and focus.
  6. The tool is simple to apply whenever we need to quickly summarize and helps us to bring a team to consensus due to its visual impact, along with the ‘In-Out’ quantification. Even if we have debates, they will be focused on specific factor relationships.
  7. In situations where we have a list of factors, but do not have objective data to substantiate the contribution of each one towards a desired effect, Interrelationship diagram helps to make initial progress.
  8. The tool is also useful when we need to quickly classify the ‘factor to factor’ cause-effect relationships as Nil, Weak or Strong.
  9. Although we may do prioritizing at a broad level based on the ‘In-Out’ arrows count, it has to be remembered that certain factors may prove critical despite have low ‘In-Out’ arrow count. The team will have to use their discretion / gather data for narrowing down such factors.
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The Quality Tools - Interrelationship diagram

The purpose of Six Sigma is to improve quality by minimizing variability. In variation reduction, several statistical methods are employed to verify the quality at different project stages. The seven management tools are used primarily for planning and managing are:

  1. The activity network diagram (AND), or arrow diagram
  2. Affinity diagram (KJ method)
  3. Interrelationship diagram
  4. Tree diagram 
  5. Prioritization matrix
  6. Matrix diagram
  7. Process decision program chart (PDPC)



Interrelationship diagram
The interrelationship diagram is a management and planning tool that displays the relationship between factors in a complicated situation. It identifies meaningful categories from a mass of ideas and is useful when relationships are challenging to determine. 


This diagram borders on being a tool for root cause identification, but it is mainly accustomed to identify logical relationships during complicated and confusing problem circumstances. In such events, the determination of an interrelationship diagram is its capability to visualize such relationships. The process of making an interrelationship diagram can help groups analyze the specific links between different aspects of an advanced situation.


An interrelationship diagram is also a tool used to prioritize issues with the most significant impact among the diagrams, which aids in making distinctions between causes and effects relationships. The affinity diagram was applied to identify the vital underlying concerns of a problem. The primary purpose of this tool is for a better understanding of the relationships between complex issues. 


The main uses of this tool are;

  • Identify or select a Six Sigma project area. 
  • Identify critical drivers that influence customer needs. 
  • Identify less significant drivers that do not significantly influence customer needs.
  • During attempting to understand connections between ideas or cause-and-effect relationships, such as when trying to identify an area of most significant impact for improvement
  • When a complicated problem is being analyzed for causes
  • When a complicated solution is being implemented
  • Consequent generating an affinity diagram, fishbone diagram, or tree diagram to explore the connections of ideas more completely
  • In root cause analysis, particularly for:
  1. Understanding how different perspectives of the problem are connected
  2. Comprehending relationships between the problem and its possible causes that can be moreover analyzed

While the affinity diagram organizes and makes various visible ideas about a project, the interrelationship diagram pinpoints logical cause-and-effect relationships between ideas. The interrelationship diagram is often constructed using an affinity diagram's components by asking, "If any section were changed, which would impact each of the other categories?" When the answer is correct for either category, an indicator is drawn from the first to the second, bestowing the cause-and-effect relationship. 


A completed interrelationship digraph is shown in the below figure. It shows the numerous issues that can impact the outcomes of a team-based constant improvement effort and how they are interconnected. This diagram could be used to recognize which components of the team process in an organization may not be working adequately well, or how there may be a lack of association between them. It may also be used to identify processes that are primary drivers from processes that are primarily driven.

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Interrelationship diagram is a visual technique which helps to understand the cause & effect relationship between various factors. This tool also helps to identify what are the various factors which helps to resolve the problem.

It can be wisely used for any problem which might be related to :-

1.    Client SLA not being met 
2.    Resolving any chronic business problem
3.    Increasing throughput 
4.    Increasing productivity 
5.    Decreasing Cost 
6.    Reducing Attrition/Absenteeism 
7.    Increase profitability 
8.    Reduction of Losses due to waste
9.    Improving Retention % 
10.    Improving Sales % 
11.    Improving TAT 

The above are some of the examples where the tool can be used. If there are any business problem this tool can help in identifying the root causes and the various outcomes . The simplicity of the tool allows to be used in any business problem and understand the relationship between various factors.

The way to use the tool is as follows :- 

1.    Create a Problem Statement 
2.    Identify factors which might affect the problem from occurring. This can be done through brainstorming or focus groups
3.    Dray the issues in a circle which was collected in the previous step  
4.    Identify cause & effect relationship 
5.    Draw a arrow to reflect direction of influence
6.    Take a count of arrows going in & out
7.    Identify drivers and outcomes – If a factor has many arrows going out then the same is a driver and if there are many arrows going in a factor then the same is an outcome.

Below is an example of Interrelationship Diagram :- 

Attrition amongst employee is very high



In the above example some of the important factors are unhappy with managers, employee don't feel valued ,employee don't see any growth opportunity ,company policy are not employee friendly, shift timings.


The effect is to search for a better job. In the above example clearly shows how an interrelationship diagram can we use effectively for any business problem. This helps to identify the various tractors as well as the affect .as the next step a team can then analyse what are the various reason which causes each of these factors .hey once the same has been identified the team can create solutions which will help in resolving each of the critical factors .  


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Interrelationship diagram is basically a cause and effect analysis. In some of the cases we have different major issues for a particular big problem/analysis. But the individual main issues/problems have no such respective defined attributes. In that case Interrelationship diagram is very much useful where we directly derive the interrelationship among all the main issues and the main issue having higher cause factor is prioritized. 

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Interrelationship Diagram is a tool that helps identify the drivers and effects (same as Cause and Effect). 


Prior to using this tool, one would need to identify the potential causes (use any of the tools - Cause and Effect Diagram or an Affinity Diagram). In C&E diagram, the relationship is well established, however, in an Affinity diagram we only get clustered categories of similar ideas. The relationships between these clusters may not be evident. Hence the need for an interrelationship diagram.


Instances where this could be used

1. Establish cause and effect relationships between lot of categories (could be a mix of multiple causes and multiple effects)

2. Establish the root cause or the cause that causes many effects. Sequencing can give us insights on this

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