Failure Mode and Effects Analysis (FMEA) describes a risk analysis method for indentifying and documenting all of the possible ways that a system or process can fail, the likelihood of the failure occurring, and the effects that such a failure would have on customers or the business.  It is often used as part of Six Sigma and other methodologies.

FMEA is an analytical approach to managing risk.  It identifies those risks which are the highest priority so that counter measures can be designed and planned ahead of time thus effectively mitigating such risks.  This prioritization is done by calculating a Risk Priority Number (RPN)

While FMEA templates may vary slightly from one to another, most contain the same basic information. 

Here is a description of how each column is used.

1. Item / Function – A high level function of categorization for which a mode of failure may exist
2. Potential Failure Mode – One possible way that the system or process can fail
3. Potential Effects of Failure – The effects or impact of the system or process failure
4. Potential Cause(s) – The cause of the potential failure
5. Severity Rating (S) – How severe the effect or outcome of the failure will be
6. Occurrence Rating (O) – How likely it is that the failure may occur
7. Detection Rating (D) – If the failure occurs, how certain is it that the failure will be detected
8. Risk Priority Number (RPN = S*O*D) – The product of the Severity, Occurrence, and Detection ratings
9. Current Controls – Any exist preventative processes that are in place to lessen the chance of the failure occurring
10. Mitigation Strategy – The action plan that will be taken if the failure occurs in order to reduce the impact that the failure has on the customer or business

The severity rating, occurrence rating, and detection rating are typically scored from 1 to 5 with 5 being the most severe rating level.  This results in higher RPN values reflecting a higher degree of priority and risk.  Therefore the highest priority item could have a potential RPN of (5 * 5 * 5) = 125.  Whereas, as score of (3*3*3) = 27 is only a moderate risk and, therefore, probably not worth planning expensive mitigation strategies.