In this blog, you’ll be learning about four lean tools for simple problem solving: 5G, 5W1H, 4M1D, and 5 Whys. In essence, these four tools create a structured approach to solving less complex problems.

An important aspect of the Lean methodology is being able to solve business setting problems. By using lean strategies, you’ll have a better chance of identifying problems, determining the root causes, and creating the most effective solutions to get the best outcomes. And if you learn how to effectively use various lean problem solving techniques, your operations can improve and become more efficient.

The Problem Solving Hierarchy

Problem solving hierarchy graph highlighting the four lean tools for simple problem solving that is being discussed in this blog

Depending on the complexity of the problem, some tools are more appropriate than others. That is to say, as the complexity of the problem increases, use the relevant tools (described above in the graph) accordingly. 

What are the Four Lean Tools for Simple Problem Solving?


The most basic and first of four lean tools for simple problem solving is 5G. Also known as the 5 Gen Methodology or the 5 Gen principle, 5G is a popular Japanese problem-solving method used for improving various manufacturing activities. That is to say, it is a tool that describes a loss phenomenon that can be related to safety, quality, parts shortage, etc. 5G is made up of five Japanese words that all start with the letter “G”: Gemba, Gembutsu, Genjitsu, Genri, and Gensoku.

The 5G Procedure
Chart depicting 5G, the first of four lean tools for simple problem solving

5W1H is the second of four lean tools for simple problem solving. Essentially, it helps contribute to the resolution of a problem by answering existing questions and triggering ideas. 

5W1H: the second of four lean tools for simple problem solving

The 5W1H questions are:

  1. 1. Who — this refers to a specific person or group of people who are relevant to the problem or situation. For example, this can include who identified the problem, who can potentially solve the problem, and who will be responsible for implementing the solution. 
  2. 2. What — when answering what, you should describe the situation and problem in detail. If possible, you should also identify the overall goal for implementing the determined solution.
  3. 3. Where — for the where, state the exact location, area, or position of the identified problem. For example, this can be at a specific pillar or machine. 
  4. 4. When — the when should include anything related to the problem that has to do with dates. For example, the timeline, deadline, duration, or any other date-related details that can help solve the identified problem.
  5. 5. Why — this is the most important element of the 5W1H method. The why details the reason and objectives for why action needs to be taken or why there’s a need to use the 5W1H method. Additionally, this last is usually asked five times to discover the root cause of the problem and to prevent it from happening again — this approach is better known as the 5 Whys analysis.
  6. 6. How — for the how, specify the steps necessary to implement the solution to solve the problem. This includes all the tools, resources, methods, and even expenses needed to carry out the plan.

4M1D, or also known as the 4M1D fishbone diagram, is the third of four lean tools for simple problem solving. In short, this is a fairly universal tool used to identify as many potential causes for a problem as possible. Moreover, it can be used to structure a brainstorming session and immediately sorts significant contributors into useful categories. The major categories of the 4M1D fishbone diagram are material, method, machine, man, and design. However, other “M’s” that may have an impact include management, money, and maintenance. In essence, the 4M1D fishbone diagram can be adjusted based on the needs of the identified problem. 4M1D is similar to the 5 Ms of Lean Manufacturing.

Example of a 4M1D fishbone diagram, the third of our lean tools for simple problem solving
The 4M1D Procedure

The procedure for conducting the 4M1D fishbone diagram is usually done with pen and paper, or on a whiteboard, and are as follows:

  1. 1. Identify a specific problem (in as little as 3-5 words) then write it at the centre right of your paper or whiteboard. Draw a box around it and then starting from the left side of the box, draw a horizontal line running across to the centre left of the page.
  2. 2. Brainstorm and determine the major categories that may have an impact on the identified problem. Then write each category as branches from the main horizontal line running across the paper or whiteboard. 
  3. 3. Brainstorm and identify all the possible causes for the specified problem and ask, “why does this happen?” As each idea is given, the leader of this analysis writes it as a branch from the relevant category. It is important to note that possible causes can be placed in more than one category. 
  4. 4. Again, ask “why does this happen?” for each cause that is written down and write down sub-causes that branch off from the main cause. Continue doing this to create a deeper understanding of the causes — the layers of branches represent causal relationships.
5 Whys

The primary goal of the 5 Whys analysis is to find the root cause of a given problem by asking a series of “why” questions five times. However, in some cases, it may take more or fewer whys, depending on the complexity of the root cause.

The 5 Whys analysis is the final of four lean tools for simple problem solving and it is one of the most powerful assessment tool of all non-statistical analyses. In short, by using this analysis, you’ll be able to identify the root cause of the problem and understand the underlying cause and effect of the identified problem. 

The 5 Whys Procedure

Listed below are the steps you should follow to complete the 5 Whys analysis:

  1. 1. Start by identifying a specific problem — what is it that you are having difficulties with? Jot this down somewhere. For example, on a piece of paper.
  2. 2. Ask why this problem has occurred and write the answer below the identified problem.
  3. 3. Continuously ask “why” to each of the successive answers you write down until you arrive at and determine the root cause of the problem.

To reiterate, again, the 5 Whys analysis may take more or fewer than 5 whys to determine the root cause. Additionally, it is important to ensure that all team members collaborating on the 5 Whys analysis agree with each of the questions being answers, as well as the root cause of the problem.