Three-dimensional numerical risk scoring systems

Three and Four Dimensional Numerical Risk Scoring Systems... 

Some risk assessment systems include numerical categories for probability and severity levels and computations are made to arrive at a number that determines the risk level. Arriving at those numerical categories is entirely judgmental. Some of those numerical risk assessment systems are discussed in Chapter 10, Three-and Four-Dimensional Numerical Risk-Scoring Systems. ... 

For this primer, two-dimensional risk assessment matrices are discussed. They are displays of variations for two categories of terms the severity of harm or damage that could result from a hazards-related incident or exposure, and the probability that the incident or exposure could occur. They also show the risk levels that derive from the various combinations of severity and probability. A review of three- and four-dimensional risk assessment systems is given in Chapter 10, Three- and Four-Dimensional Numerical Risk-Scoring Systems. ... 

In Chapter 10, Three- and Four-Dimensional Numerical Risk-Scoring Systems, comment is made on FMEA publications issued for the semiconductor industry by International SEMATECH and for the auto industry by the Automotive Industry Action Group. 

THREE AND FOUR DIMENSIONAL NUMERICAL RISK SCORING SYSTEMS... 

However, the world of risk assessment is in transition. Some systems now in use are three- or four-dimensional, and they require numerical risk scorings. Safety professionals can expect that variations of numerical risk scoring systems will proliferate. Nevertheless, it needs to be said that two-dimensional, qualitative risk assessment systems are not obsolete. Often, a two-dimensional system will be selected because it is sufficient for the hazards and risks encountered and it works well within an organization. This chapter will inform safety professionals on ... 

Three-dimensional numerical risk scoring systems... 

An extended three-dimensional numerical risk scoring system that includes a method to justify the risk amelioration costs in relation to the amount of risk... 

Similarly, some engineers are using numerical risk scoring systems to meet the risk assessment requirements placed on manufacturers who sell machinery to countries in the European Community. One such system in use for that purpose is four-dimensional. Also, a three-dimensional numerical risk-scoring system is in use in a segment of the heavy machinery manufacturing industry. It was introduced by engineering personnel to meet the demands for product safety. 

Substantial variations exist in the elements to be scored in the three-dimensional and the single four-dimensional numerical risk scoring systems to be reviewed here. To begin the discussion, excerpts are taken from the National Safety Council s (NSC s) Accident Prevention Manual Administration Programs, Twelfth Edition, and appear here with permission. 

THREE AND FOUR DIMENSIONAL NUMERICAL RISK SCORING SYSTEMS TABLE 4 Suggested Design FMEA Severity Evaluation Criteria ... 

A MODEL THREE-DIMENSIONAL NUMERICAL RISK-SCORING SYSTEM... 

The goal was to create a three-dimensional numerical risk-scoring system that serves the needs of those who are more comfortable with statistics in their risk assessments, addresses the strong beliefs of those who want frequency of exposure given separate consideration in the risk assessment process, and maintains credibility and efficacy. An example demonstrating how the risk-scoring system is applied appears in Table 26. 

Three-dimensional numerical risk-scoring systems can be crafted that have credibility. But, how should such systems be used Numerical risk scores carry an image of precision that can influence decision making and priority setting. In reality, however, they should not be the sole or absolute determinant. 

Although three- and four-dimensional risk scoring systems are now more commonly used, there are several reasons to be inquisitive and cautious concerning their content, the meanings of the terms used in them, the numerical values applied to the gradations within elements to be scored, and how they are applied in determining risk levels. 

In the process, for each identified hazard, numerical scorings as follows are given to Severity, Exposure, and Probability. It is significant that they are totaled to arrive at a final rating, not multiplied in sequence as is the case in other three- and four-dimensional risk-scoring systems. Thus, the status of the severity... 

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