# Presentation: 708951

## Risk, Probability and Judgment

## 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?

- Risk, Probability, and Judgment

- The Harnessed Atom

## Making Informed Decisions

- Define the problem or choice
- Gather information
- Evaluate the information
- Make a decision

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## Slide 6

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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?

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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.

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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.

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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.

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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.***

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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.

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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?

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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

- Risk, Probability, and Judgment

- The Harnessed Atom

## 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?

- Risk, Probability, and Judgment

- The Harnessed Atom

## Words to know

- Benefits
- Biased information
- Consequences
- Human-made risk
- Natural risk
- Probability
- Percentage
- Risk assessment
- Risks
- Societal decisions
- Values

- Risk, Probability, and Judgment

- The Harnessed Atom