Normalized Risk

Measure of risk created by mathematically adjusting a value in order to permit comparisons.

Sample Usage: The risk assessment report displayed the normalized risk of the three biological agents to facilitate comparison and avoid sharing sensitive information.


  1. Typically, normalized risk divides the risk of each scenario by the sum of the risk across the set of scenarios under consideration. For example, if you are considering the expected number of fatalities from three different biological agents A, B and C, then the total risk posed by these biological agents is the sum of the risk posed by each of them. If agent A has expected fatalities of 10,000, Agent B has 7,000, and Agent C has 3,000, then the total risk is 20,000 fatalities and the normalized risks are 0.5 for Agent A, 0.35 for Agent B, and 0.15 for Agent C. This particular way of normalizing risk is commonly referred to as ―normalizing to 1‖ because now the risk from all the scenarios in the considered set sums to 1.
  2. Risk can be normalized by dividing by an existing sample space value. For example, if there were 100 car accidents this year and 800 last year, then normalizing these values with respect to the total vehicle trips each year permits a more appropriate comparison of the risk of last year versus this year. If there were 10,000 vehicle trips this year then 100/10,000, or 1% of all trips ended in accidents, whereas if last year there were 100,000 vehicle trips then 800/100,000, or 0.8% of all trips ended in accidents. Without normalization it would appear that it was more risky to drive last year, but in reality the opposite is the case.

Source: DHS Risk Lexicon, U.S. Department of Homeland Security, 2010 Edition. September 2010 Regulatory Guidance

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