Root Cause Analysis

Posted by on Oct 12, 2012 in Continuous Improvement, Problem Solving | 0 comments

Root cause analysis is the part of problem solving that tries to determine the root cause(s) of problems or anomalies that effect processes.  It focuses on getting to the root cause and implementing corrective action versus addressing only the symptoms of a problem.  The action of focusing on the root cause and implementing corrective action thus prevents the problem from reoccurring.

Problems may have more than one root cause and it’s important to understand that and have the perseverance to identify them all in order to prevent the problem from coming back.  How the problem is defined makes a big difference and a good problem statement can help tremendously.

There are several methods or processes that address root cause analysis, such as the 8D Problem Solving Process, 5-Step Process, etc.  The following is a general process for determining root cause:

  1. Obtain all the information and data you can concerning the problem.  Define the problem and develop a good problem statement.  If possible, use a control chart to determine if you are dealing with common cause or special cause variation.  Another great tool I have used many times to help with clue generation is the Is, Is-Not.
  2. Develop a time line for the events that led to the problem.  Placing events in chronological order can help you make sense of the issue and put it into perspective.
  3. Use the 5 Why tool to identify the causes associated with each step in the sequence towards the defined problem.
  4. Identify all the factors that may have contributed to the problem.  Use the 6Ms, i.e., Man, Machine, Method, Material, Measurement, and Mother Nature to help you identify the factors.
  5. Identify corrective actions that would prevent recurrence.
  6. Identify solutions.  These solutions should be those that can be implemented quickly and are the most effective and least costly to implement.
  7. Implement the solutions and ensure they are effective.
A good way to know for sure if you have the true root cause(s) is if you can turn the problem on and off.  This is recommended if you have the luxury of being able to do it.
Other useful tools that can help you in collecting and analyzing data and information are:
  • Histogram and box-plots for variable data.  Always plot the data you have.
  • Pareto charts for attribute data.
  • Control charts to determine if special causes are present.
  • Check sheets
  • Pictographs or concentration diagrams
  • Cause and effect diagrams
  • Data stratification
  • Comparison of extremes
  • PDCA

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