Risk Acceptability
Safe does not
necessarily mean
„free from risk‟
Session 21 1
Most Risks have
Associated Benefits
Session 21 2
“Acceptable risk is the risk
associated with the best of
available alternatives, not with
the best of alternatives which we
would hope to have available.”
Source: Derby, Stephen L., and Ralph L. Keeney, 1981.
Session 21 3
Factors that Determine Risk
Acceptability
• Personal
• Political / Social
• Economic
Session 21 4
Injustices
• The process of determining the acceptability of
risk can be influenced by those with money and
vested interests.
• Setting a dollar figure (in cost-benefit analyses)
on a human life is considered by many to be
unethical and unconscionable.
• Risk management is usually an undemocratic
process, as those who may be harmed are not
identified or asked if the danger is acceptable to
them.
Session 21 5
Risk Acceptability Assessment
Methods
• “No Go” Alternative
• Accept the Risk
• Establish a “De Minimis Risk” Level
• Establish a “De Manifestis Risk” Level
• Perform a Cost-Benefit Analysis
• Perform Cost Effectiveness
• Choose the Best Choice Among Alternatives
Session 21 6
Derby and Keeney‟s 5 Steps
• Define the alternatives
• Specify the objectives and measures of
effectiveness to indicate the degree to which they
are achieved
• Identify the possible consequences of each
alternative
• Quantify the values for the various consequences
• Analyze the alternatives to select the best choice
Source: Derby and Keeney, 1981
Session 21 7
COST
Example A
•K
•L
*M
0
0 RISK
Source: Derby, Stephen L., Ralph L. Keeney. 1981. Risk Analysis: Understanding “How Safe Is Safe Enough?” Risk Analysis. V.1.
No.3. Pp.217-224.
Session 21 8
COST
Example B
Minimum Risk
•K
Minimum Cost
•L
0
0 RISK
Source: Derby, Stephen L., Ralph L. Keeney. 1981. Risk Analysis: Understanding “How Safe Is Safe Enough?” Risk Analysis. V.1.
No.3. Pp.217-224.
Session 21 9
COST
Example C
*M
•K
•L
*
0
0 RISK
Source: Derby, Stephen L., Ralph L. Keeney. 1981. Risk Analysis: Understanding “How Safe Is Safe Enough?” Risk Analysis. V.1.
No.3. Pp.217-224.
Session 21 10
COST
Example D
Case 1
•K
•L
Case 2
0
0 RISK
Source: Derby, Stephen L., Ralph L. Keeney. 1981. Risk Analysis: Understanding “How Safe Is Safe Enough?” Risk Analysis. V.1.
No.3. Pp.217-224.
Session 21 11