Wiley Handbook of Science and Technology for Homeland Security, 4 Volume Set

QUALITATIVE REPRESENTATION OF RISK*

GARY R. SMITH

Logical Decisions, Fairfax, Virginia

JAMES SCOURAS

Defense Threat Reduction Agency, Ft. Belvoir, Virginia

ROBERT M. DEBELL

Gaithersburg, Maryland

1 INTRODUCTION

A risk representation is an attempt to describe or clarify a particular risk. A qualitative risk representation describes or clarifies without the explicit use of numbers. A qualitative risk representation can be used to communicate the results of a qualitative risk assessment or summarize a quantitative risk assessment. Qualitative risk representations can be used to describe individual risks or to compare the relative severity of different risks.

Risk can be defined as the potential for injury or loss. This definition has two parts: the potential (or likelihood) and the loss (usually called a consequence in risk analysis). Quantitative representations describe likelihood with probabilities and loss using numeric scales such as dollars or fatalities. Alternatively, qualitative representations can be used for the likelihood, the loss, or for the risk as a whole.

All risk representations are subject to misinterpretation. This can be due to poor definition of the risk being represented or lack of caveats regarding the underlying analysis. Qualitative risk representations are further subject to misinterpretation due to the imprecision inherent in language and due to imperfect alignment between qualitative representations and underlying quantitative assessments. It is also ...