Tools and methods for root cause analysis
5 Whys
So why 5? 😉 Actually there is no special magic in number five .. but the general idea is to dig deeper below the surface.
As we dig deeper into the problem using the “why” question over and over again, we are allowed to get to the root of the problem. Sometimes we have to ask less than five “why” and sometimes more – here is how the actual method works:
(1) Why did the customers not eat the dish? Because she had no taste for them.
(2) Why was it not tasty? Because the taste felt weird.
(3) Why did the dish taste strange? Because the refrigerator did not cool it properly.
(4) Why did the refrigerator not maintain the required cold? Because it was not connected to electricity.
(5) Why was the refrigerator not connected to electricity? For the apostle stumbled on his electric wire.
(6) Why did the apostle stumble on the power cord? Because the wire is on the floor and crosses the aisle.
(7) Why is the wire in the aisle? Because there is no active plug on the side of the room where the refrigerator stands.
The elegance of this method lies in its simplicity. All you have to do is ask “why?” For any previous answer. The weakness of the method lies in the fact that the conclusion depends on the previous answer. It is important to be careful and make sure that the answers do not produce a confirmatory bias.
Ichikawa
Method: Refers to the processes used.
Material: Can refer to raw material, components and supporting materials.
Manpower: Can include training and skill set as well as number of resources.
Machines: can include those directly related to the process as well as the supporting equipment.
Measurements – Measurements: include the data as well as the equipment, test methods, calibration and quality controls designed to produce measurements.
Milieu – Environment: Can include the humidity levels, temperature, noise, vibration and other characteristics of the space where the problem appeared.
The team will brainstorm all the information and data, consider all the facts related to the situation, and then point out the factors directly involved in the problem.
Chronology – an overview of events and factors
In this approach, the team researching the roots of the problem will trace the process that led to the problem, not with the help of the question “why?” But with the question “What happened next?” The team will go through the process at least twice. First with a smooth page, and then with a copy of the procedure.
Go through the process that led to the problem. Do not judge the answers, just write them. Ask verifying questions like “Did you do anything before this step”? It is important to get accurate answers and remember that employees often tend to say what they were supposed to do. Be patient and do not react when you hear that a procedure was not performed accurately.
After verifying the interview, decide if there were any sub-processes that require a similar in-depth investigation. After completing all the interviews move on to the next step.
Next you will go through with the interviewed employee about the procedure as it is written and worded. At each step they asked, for example: “The procedure says you have to mix twenty minutes before adding the next ingredient. You added all the ingredients before you mixed. I’m right”? Notice all the places where the employee acted in accordance with the procedure and all the points where there were anomalies. Be kind and pleasant to the employee who provides you with information. A relationship that has a high level of trust will yield effective results time and time again.
After completing the interviews review the steps or steps that included anomalies to determine if any of them might have created the problem that was discovered. Follow-up interviews will help determine if additional guidance or training is needed or perhaps additional process controls, whether the procedure is deficient, or whether there is additional corrective action to suit the situation.