Qualitative risk measurement

Risk Indices - A risk index is a single-number measure of tlie risk associated with a facility. Some risk indices are qualitative or semi-quantitative, ranking risks in various general categories. Risk indices may also be quantitative averages or bencluiiarks based on otlier risk measures. 

Even for the large organization with significant annual hours worked, in addition to historical data, hazard-specific and qualitative performance measures are also necessary, particularly to identify low probability-severe consequence risks. 

An evaluation of both the frequency and the consequences of potential hazardous events to make a logical decision on whether the installation of a particular safety measure can be justified on safety and loss control grounds. Frequency and consequences are usually combined to produce a measure of risk, which can be expressed as the average loss per year in terms of injury or damage arising from an incident. The risk calculations of different design alternatives can be compared to determine the safest and most economical options. Calculated risk may be compared to set criteria that have been accepted by society or required by laws. See also Qualitative Risk Analysis. 

Qualitative risk evaluation and recommended control measures... 

The Situation B method limits housing to sites that are up to Amber 2 unless the risk assessment can demonstrate that housing would be acceptable. The Situation A method does not do this, but it does require a comprehensive qualitative risk assessment to justify the gas protection measures for any characteristic situation above 3. The two methods are therefore similar in this approach. 

In this chapter, the methodological framework is provided for the developed model, which detects and ranks the complexity of ship-ship encounters. First, the available micro-level ship traffic data, as obtained from the Automatic Identification System (AIS), is outlined. Subsequently, the process and outcome of an expert elicitation related to the development of a quantitative Risk Indicator (I). The latter is a measure of risk in the sea area, based on detection of vessels encounters and their complexity. Then, the mathematical formulation of the indicator is presented, both in regards to the model structure and model parameters. Finally, the obtained results need to be clustered to arrive at qualitative Risk Indicator. Thus, the purpose and rationale of the applied clustering technique is outlined. 

In addition to the qualitative uncertainty assessment, the risk description by Flage and Aven (2009) also considers sensitivity S, which relates to the change in the relevant calculated risk measures conditional to changes in the uncertain quantities. This leads to a risk description ... 

Apart from the probabilistic risk measurement, a sensitivity analysis is made, identifying the elements in the model to which the risk measure is most sensitive. For those probabilities to which the model is most sensitive, a qualitative assessment of the strength of justification and the direction of bias is made. Finally, the sensitivities, strengths of justification and (when relevant) the direction of biases are grouped in a set of matrices, showing the overall picture of sensitive model elements and their epistemic and non-epistemic justification. 

A decision maker could utilize this qualitative assessment along with the quantified risk measures based on probabilities to evaluate how confident he can be about the risk measures. When e.g. an ALARP decision criterion is applied for evaluating the risk acceptability, the broad qualitative assessment guides the decision maker in establishing that the risk is positioned in a given area. 

Arbitrary categories have been established in MIL-STD-882 that provides qualitative measures for the most reasonable likelihood of occurrence of a mishap and for the outcome severity of a mishap. For example, if the safety analyst assesses that an event will occur frequently, it is assigned an index level A, or if it occurs occasionally, it is given an index level C. This qualitative index value is then used in qualitative risk calculations and assessments. 

Provides a qualitative measure of risk Provides a coarse quantitative measure of risk Provides an absolute quantifalnc measure of risk... 

In this paper I have tried to show that measurement of health benefits attributable to TSCA is not feasible. I hope that in doing so I have not belabored the obvious. For new chemicals and for most existing chemicals, prospective evaluation of health benefits to be achieved by various exposure controls will have to be based on extrapolation from microbial and animal data. However, while such extrapolation may be useful in a qualitative sense, quantitative risk assessment techniques involve considerable uncertainty, and in any case have not been developed for chronic effects other than cancer. 

The quantitative evaluation of expected risk from potential incident scenarios. It examines both consequences and frequencies, and how they combine into an overall measure of risk. The CPQRA process is always preceded by a qualitative systematic identification of process hazards. The CPQRA results may be used to make decisions, particularly when mitigation of risk is considered. 

Process Hazard Analysis— An organized effort to identify and evaluate hazards associated with chemical processes and operations to enable their control. This review normally involves the use of qualitative techniques to identify and assess the significance of hazards. Conclusions and appropriate recommendations are developed. Occasionally, quantitative methods are used to help prioritize risk reduction measures. 

The assessment endpoint should be not only measurable (at least potentially) but also modelable. Defining a modelable endpoint is likely to require close discussion between an assessor (who knows what they can model) and a risk manager (who knows what they want to protect). Sometimes the assessment endpoint is only indirectly related to the management goal, for example, if the assessment endpoint is a risk to individuals, but the aim is to protect population sustainability. In such cases, qualitative inference will be required to interpret the assessment result. This inference will need to be done jointly by the risk assessor and risk manager. It is likely to involve substantial uncertainty, which will have to be taken into account qualitatively when producing a narrative description of the assessment outcome. This step should be identified as part of the conceptual model. 

The above discussion reveals that all elements of risk associated with critical information infrastructure are rated as very high . Consequently, we can safely qualitatively assert that the risk itself is very high . This recognition leads inevitably to the conclusion that critical information infrastructure must be protected. Moreover, its protection is critical. The question then is how do we go about protecting critical information infrastructure Clearly, the answer to this question is multidimensional, ranging from policies to strategies to measures. In the next section we will attempt to answer the question at the policy and strategy levels. 

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