1. Risk, Probability and Judgment

2. The Harnessed AtomRisk, Probability, and Judgment 2 Today’s Topics What is risk? How do we perceive risk? How do we measure risk? What is risk assessment? How does risk affect our decision making?

3. The Harnessed AtomRisk, Probability, and Judgment 3 Making Informed Decisions 1.Define the problem or choice 2.Gather information 3.Evaluate the information 4.Make a decision

4. The Harnessed AtomRisk, Probability, and Judgment 4 Energy Decision-making Each source of energy has trade-offs –Some good things, some bad things associated with each –Most people feel that having abundant energy is worth some risks

5. The Harnessed AtomRisk, Probability, and Judgment 5 What is Risk? Risk is essentially the chance that something bad could occur Everything we do exposes us to some risk –Walking across the street –Going down a flight of stairs –Driving around the block –Playing sports –Generating electricity

6. The Harnessed AtomRisk, Probability, and Judgment 6

7. The Harnessed AtomRisk, Probability, and Judgment 7 Risks of Nuclear Energy All energy sources have related risks Questions to be answered about nuclear energy: –Do the benefits outweigh the risks? –How do the risks of nuclear energy compare to risks related to using other sources to generate electricity? –What are the risks of not using/having electricity?

8. The Harnessed AtomRisk, Probability, and Judgment 8 Judging Risk Today, we know a lot about many kinds of risks –Advances in science –Availability of information through mass media As individuals and groups we make decisions based on how risky we think certain things are Different people see different things as dangerous or acceptable

9. The Harnessed AtomRisk, Probability, and Judgment 9 How We Perceive Risk A variety of factors influence how risky we believe certain activities to be –Control –Dread –Natural vs. man made –Familiar vs. new –Choice –Awareness –Sudden vs. gradual

10. The Harnessed AtomRisk, Probability, and Judgment 10 Risk Assessment A branch of science that determines actual risks involved in various technologies and activities Aimed at protecting public health and improving public safety Scientists and decision-makers compare risks by looking at their relative probabilities.

11. The Harnessed AtomRisk, Probability, and Judgment 11 Probability Probability is a number that quantifies how likely something is to occur Percentages and probabilities are related but not the same. –Percentages are a mathematical statement of how many times out of 100 something happens. –Probabilities refer to just one occurrence.

12. The Harnessed AtomRisk, Probability, and Judgment 12 Probability Scientists determine probabilities through repeated observations or controlled experiments The number of times that a specific outcome occurs, divided by the total number of times the experiment is repeated, is the probability that the specific outcome will occur.

13. The Harnessed AtomRisk, Probability, and Judgment 13 Probability Random events like flipping a coin cannot be predicted with certainty. –Every time the coin is flipped, there is a 0.50 probability of heads and a 0.50 probability of tails. –If a lot of flips in a row land heads up, the probability that the next flip will be tails is still 0.50.

14. The Harnessed AtomRisk, Probability, and Judgment 14 Calculating Probability Then the probability of each outcome is 1 divided by the number of possible outcomes. –For example: the probability of drawing the ace of spades from an ordinary deck of cards is 1/52.

15. The Harnessed AtomRisk, Probability, and Judgment 15 Think about it… What is the probability of drawing any ace on any one draw? What is the probability of drawing 5 cards of the same suit?

16. The Harnessed AtomRisk, Probability, and Judgment 16 Health and Safety Risks It is often harder to determine probability of health and safety risks for people –May not be enough information –May not be possible to test all aspects of the system Certain are rules used to make reasonable predictions

17. The Harnessed AtomRisk, Probability, and Judgment 17 Health and Safety Risks Rules used by decision makers for determining what is “safe” –One in a million Does not increase the health risk of the population by more than one chance in a million –ALARA As low as reasonably achievable

18. The Harnessed AtomRisk, Probability, and Judgment 18 Health and Safety Risks Limitations to knowing risk: –To know risk of “new” technology, we need to know what risk was before –Risk studies are often based on studies of large numbers of animals Biological differences between rats and mice and humans Not socially acceptable to test things on large numbers of humans

19. The Harnessed AtomRisk, Probability, and Judgment 19 Accepting Risk Deciding on whether a risk is acceptable involves weighing consequences and values Sometimes it is very expensive to reduce the risk even a small amount

20. The Harnessed AtomRisk, Probability, and Judgment 20 Making Societal Decisions Many questions—none of them simple –What is the consequence of the risk—loss of money, illness, or death? –How large are the consequences? (costs, number of people affects, size of environment effected) –Do the risks and benefits fall on different people? –Do the risks fall on the decision-makers or on others? –How are decisions made? –What are the alternatives?

21. The Harnessed AtomRisk, Probability, and Judgment 21 Words to know Benefits Biased information Consequences Human-made risk Natural risk Probability Percentage Risk assessment Risks Societal decisions Values