We are constantly making decisions
based on our capacity
to handle different levels of risk.
Our understanding of risk
is based on past experience
and our notion
of potential outcomes.
But, helping individuals chose
their level of acceptable risk for
any given hazard is critical.
Quantifyingthese levels of risk
“perception” can be
challenging.
However, not all risk is economically
or easily quantifiable.
How do you place a value on
your own life or
the loss of a loved one?
To explore the perception of risk in the “language ofprobabilities”, we posed a series of questions to students who were learning about hazards.
The Question we posed:
Given the probability X of
an earthquake of magnitude Y,
would you drive across a bridge?
(If not, the alternative is to drive 1 hour
out of your way).
For example, if there was a
25% chance of a M 4.0 earthquake, would you cross the bridge?
Magnitudes. No assumptions were made about student familiarity with Magnitudes and the associated damage. Theyrelied on what they heardin the media.
Probabilities. The students only knew that 30% probability meant that one third of the time there is a quake when the “conditions” were similar.
These questions were meant to provide a baseline to see what they understood about these hazards from the media, academic and government sources to help us see if improvements could be made in the messaging.
P ( X | Y )X = probability of occurrence
Y = earthquake magnitude
Several probability levels for
earthquakes of different magnitudes
were asked.
ResultsThe Results are interesting...
Major Outcomes:
The greater the magnitude the less likely they are to cross the bridge.
The greater the probability the less likely they are to cross the bridge.
Most students understood probabilities,but some misunderstood the terms altogether.
3
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
M3 M4 M5 M6 M7
25%
50%
75%
Results show the probability of earthquake
occurrence needed to invoke a response.
Earthquake Magnitude
Perc
ent
of
Ind
ivid
ual
s C
ross
ing
Bri
dge Probability of
Earthquake Occurrence
99 students
Consistent with literature:
Others* have shown similar risk distributionsfor other hazards and situations.
*See Jonkman, vanGelder and Vrijling, 2003, An Overview of of quantitative riskmeasures for loss of life and economic damage, J Haz Mat A99 (1-30).
Severity of hazard or accident
Probabilityof exceedance
Unacceptablerisk
Acceptablerisk
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
M3 M4 M5 M6 M7
25%-female
25%-male
50%-female
50%-male
75%-female
75%-male
Earthquake Magnitude
Perc
ent
of
Ind
ivid
ual
s C
ross
ing
the
Bri
dge
Perceived Risk by Gender
25%
Probability of Earthquake Occurrence
75%
50%
68 females31 males
Our population showed gender-specific risk sensitivity.
Males took progressively more risk than females as the probability of an event increased.
One could argue for a biological link to testosterone levels in regulating the hypothalamus-pituitary-adrenal levels in flight-fight response.*
*Mehta, Jones, and Josephs, 2008, J Pers Soc Physhol 94(6): 1078-93.
We tackled a new situation:
New hazard: Landslides
Added a new factor: Responsibility
We posed 2 questions to see howmuch a response is affected byresponsibility.
The Question.
At what probability would you NOT cross the bridge?
0 10 20 30 40 50 60 70 80 90 100%
Landslidewill not happen
Landslidewill definitely
happen
Probably will
happen
Probably will nothappen
If they answer 40%:
At what probability would you NOT cross the bridge?
0 10 20 30 40 50 60 70 80 90 100%
Landslidewill not happen
Landslidewill definitely
happen
Probably will
happen
Probably will nothappen
acceptable risk unacceptable risk
The Question.
At what probability would you NOT cross the bridge ifyou had a child in the car?0 10 20 30 40 50 60 70 80 90 100%
Landslidewill not happen
Landslidewill definitely
happen
Probably will
happen
Probably will nothappen
Although the hazard remained the same, the perception of risk increased asthe subjects took on responsibility(such as travelling with a child).
For high probabilities of landslide occurrence:Significantly fewer students would cross the bridge when given more responsibility.
Results
Simple questionnaires can be given to user
groups to understand their perception of risk
for any situation.
This has important implications for effective
communication and messaging
in hazard preparedness.
The Take-Away
Custom Messages. Messages can be tailored
to the level of hazard and perceived risk.
Probabilities. Messaging with probabilities is
perhaps best explained in simpler terms
(e.g. high, medium or low).
Designed by Stakeholders. The most effective
messages and graphics can be designed by
stakeholders to ensure clarity.
The Take-Away
A tsunami warning where the message is simple and visual.
But it doesn’t cover tsunami that are createdremotely.
A Note about this study.
The data and plots are meant to show a trend for the given population of students and are not meant to be representative of a larger population.
Factors such as age, religion, educational level, and other indicators may contribute to subjective biases in how individuals respond in the presence of a hazard.
This preliminary study shows that there are quantitative ways to measure qualitative information.
As in any study, care must be given in presenting a statistical problem to individuals who are not familiar with probabilities and this topic will be explored further.
- Michael Kozuch( 2015)