Problem statement

The problem statement objective is to organize the information that justifies the root cause analysis. During this stage the technical terminology plays a key role to ensure that all members of the problem solving team receive the same message. The following problem solving techniques are generally used in this stage:

Flowcharts

Pareto charts

Scope definition

Data collection

Problem appraisal

Diagnosis

The diagnosis task uncovers the root cause, not the precipitating or remote cause. In the cause-effect chain, we define precipitating causes as the causes usually closer to the effect and remote causes as the causes remotely responsible for the effect. The following example describes these concepts:

"An explosion (precipitating cause) may have caused a fire (the effect). The gas leak that caused the explosion (a remote cause) was the result of a defective gas pipe (root cause), which was installed several years ago."

We normally apply the following problem solving techniques during the root cause analysis in the manufacturing organization:

Why-why diagram

Differential analysis

Affinity diagram

Cause and effect diagram

Verification

The verification activity of the problem solving techniques takes place before we invest valuable resources in the solution generation. The verification tools ensure that we provide an objective, immediate, qualified, and timely confirmation that we identified the root cause (s). The root cause verification includes at least the application of the following tools:

Analysis of variance

Logical tests

Statistics hypothesis testing

Regression analysis

Solution generation

This is the creative phase to develop several possible solutions. It is also a preventive task that contributes to avoid new problems. Once the best solution is selected, we will look at the system and thoroughly review its application to other processes. The basic tools that we may apply are:

Systematic diagram

Risk assessment

Consensus

Standardization

Validation

We examine the results of the implementation to validate that the customer, technical, process, and product requirements are satisfactorily met. We usually use quality tools such as:

Control charts

House of quality

Matrix diagram

Field experiments