What Six Sigma did for quality is beginning to be applied to industrial safety. The same desire to eliminate product mistakes is at work to reduce injury rates. In this parallel journey there are six levels, or Six Sigma in safety. Each “sigma control” builds on the previous level until the sixth sigma—a zeroinjury culture—is attained.
One Sigma Control: “Reacting”
One sigma is set in the era of the three E’s of safety: engineer, educate, and enforce. The tools for these rudimentary safety mechanics include work orders, safety rules, injury investigations, and
compliance programs. While barely touching the surface of why injuries occur, one sigma tools
nonetheless lay the foundation in establishing a safe workplace. As with one sigma in quality, the
performance—conceptually, at least—is 68.5 percent error-free. This first level represents the ability
to sustain the essentials in worker safety.
Two Sigma Control: “What we see”
The tools for two sigma control include observation programs, job safety analyses (JSA), and nearmiss reporting. At this level, awareness and analysis tools are applied to reach a two sigma level or injury-free rate of about 98.5 percent. Research indicates that a 10 percent error level requires
roughly 3000 observations to detect and act on mistakes (Harry 1998, 2000; Walmsley 1997).
As errors decrease, more observations are needed to detect the incorrect activities, which means
a 1 percent error level requires about 10,000 observations to be statistically valid (Petersen 1993).
It’s a benchmark that underscores just how challenging it is for companies to move beyond two sigma control without adding to its traditional safety repertoire of observation programs and “rearview mirror” reporting. Two sigma safety control is focused on “what we see” in the workplace.
Three Sigma Control: “What we do”
Three sigma product quality requires well-defined responsibilities and accountabilities to provide predictable results on a regular basis. The same is true for three sigma safety. Without safety accountability at all levels, the possibility for companies to attain this level is next to impossible.
Organizations that have been able to move from two- to three sigma, have generally attributed their
success to the introduction of individual accountabilities into their safety programs. Embracing the
conventions of accountability and personal responsibility is a critical factor in achieving a workplace
that is 99.7 percent injury-free. While three sigma is commendable, companies are still incurring
lost-time injuries at a rate of 3 per 1000 employees. Three sigma safety addresses “what we do” in the workplace.
Four Sigma Control: “What we believe”
Beginning in 1979, Dan Petersen teamed up with Charles Bailey to develop a comprehensive and statistically validated safety perception survey on behalf of the U.S. rail industry (Bailey 1993, 1988;
Bailey and Petersen 1989). Today, the survey system is used to audit an organization’s safety culture
and identify perception gaps across 20 categories, cross-tabulated by management, supervisors, and
front-line employees. The self-administered questionnaire includes 73 questions and provides companies with a statistically reliable method to answer the questions, “Where do our people believe we are weak?” and “Where do they agree and disagree?” Today’s safety perception survey results can
be compared with a database that combines more than two million respondents. It’s a tool that provides statistically valid data for industry-wide comparison analyses.
The survey system breakthrough added an important dimension to pinpoint opportunities. Not
only does it identify safety shortcomings, its implementation is recognized as an invaluable “buy-in”
mechanism to set the stage for continuous improvement work teams—a necessary component to
reach four sigma control: 99.97 percent injury free. Four sigma control concentrates on the nonobservable “What we believe” in workplace safety.
Five and Six Sigma Safety Control: “How we engage and how we lead”
The next challenge is to utilize the data in the previous four levels of safety:
• The fundamentals: injury and work order data
• Observable processes
• Accountabilities of what we do
• Information on what we believe from a safety perception survey