A numerical value is then assigned to the severity of
the failure (S), the frequency of occurrence (O) and the
detectability of the failure (D). These numbers are multiplied
to;give;the;RPN.;The;RPN;is;an;index;that;gives;the;relative
quality risk associated with each failure mode. 10
With the FMEA table completed (see Table 2), steps in the
process that present the greatest challenges to cookie quality
can;be;identified;by;comparing;their;relative;RPNs.;The;steps
with the highest numbers are the biggest risk to quality. A cross-functional team can then decide at what level they will consider
an;RPN;acceptable.;In;this;example,;the;cutoff;number;that
will be used for the cookie process will be 45. A potential
failure with a number greater than this is deemed unacceptable
and that step in the process must be improved. A good way to
visualize these relative risks is with a Pareto diagram, the chart
created by economist Vilfredo Pareto. This diagram is a simple,
easy-to-use method of visually representing which problems
are the most vital to quality. 11 A Pareto diagram of quality risks
in the frozen cookie production process will point out which
problems should be addressed first to improve the quality of
the cookies (Figure 2).
Unfortunately, this Pareto diagram generated from the
risk assessment table does not give a useful differentiation
of the “vital few” problems that need to be addressed in the
