Numbers and their uses
Chapter 2 - Understanding Numbers
Section 2.3 - Risk Assessment
" If it were up to me to add some classes to the grade school
curriculum, I think I'd put more emphasis on these skills: public
speaking, risk assessment, bullshit detecting, social skills,
decision-making, managing your own body, and influencing people. "
Dilbert Blog - Smarter Than a 5th Grader
The ability to calculate risk is what distinguishes the smart from the not
As Dilbert humorously put it, risk assessment is a
critical skill that is overlooked by traditional school education. In
the previous section we discussed how really small numbers can often be
treated the same. However, in this section we are going to learn that
differences in really small numbers can mean the difference between life
First, what do we mean by risk assessment? Risk
assessment is the ability to internally calculate the likelihood of
occurrence based on the cumulative probabilities of many interaction
conditions occurring simultaneously over a period of time.
Read the following article that appeared in The New
Yorker by eminent surgeon, Dr. Atul
Gawande. In the article, Dr. Warwick is explaining to his Cystic
Fibrosis patient, Janelle, why experimenting with skipping medication is a
bad idea even
though it appears to not make any difference.
"Let's look at the numbers, he said to me, ignoring Janelle. He went to a
little blackboard he had on the wall. It appeared to be well used. A
person's daily risk of getting a bad lung illness with Cystic Fibrosis (
CF ) is 0.5 per
cent. He wrote the number down. Janelle rolled her eyes. She began
tapping her foot. The daily risk of getting a bad lung illness with CF
plus treatment is 0.05 per cent, he went on, and he wrote that number
down. So when you experiment you're looking at the difference between a
99.95 % chance of staying well and a 99.5 % chance of
staying well. Seems hardly any difference, right? On any given day, you
have basically a 100 % chance of being well. But, he paused
and took a step toward me, it is a big difference. He chalked out the
calculations. Sum it up over a year, and it is the difference between an
85 % chance of making it through 2004 without getting
sick and only a 15 % chance.
He turned to Janelle. How do you stay well all your life? How do you
become a geriatric patient?, he asked her. Her foot finally stopped
tapping. I can't promise you anything. I can only tell you the odds.
In this short speech was the core of Warwick's world view. He believed
that excellence came from seeing, on a daily basis, the difference between
being 99.5 % successful and being 99.95 % successful. Many
activities are like that, of course: catching fly balls, manufacturing
microchips, delivering overnight packages. Medicine's only distinction is
that lives are lost in those slim margins.
Let us look at another example of how to apply risk assessment to
determine a safe speed to drive. Look around the next time you are on the
road and you will notice at least 85% of your fellow motorists ignoring
the "3 second rule," which requires a minimum of 3 seconds to
for reaction time, steering time, brake application and braking distance
in case of the unexpected. It gets ignored one way or another on every
street at every speed, every day.
Motorists who ignore the three second rule
are confusing dumb luck with skill during every commute.
Most of these motorists are choosing a
1 or 2 second rule at best; a recipe for an unavoidable crash,
especially in fog. To heed the 3 second rule at 70 Mph ( 110 Kmh ),
one must back off over 100 yards. Most people
follow at only a few car lengths while ignoring the laws of physics.
Instead they rely on their perception of supernatural braking power or
angels overhead. Neither are respected by
Murphy and his law.
Those who apply rational and predictive driving skills
behave the opposite of the speed-at-any-cost mentality. Once a person
truly comprehends risk, a
calmness takes over, speeds drop and following distances
increase. It is a rare thing to see: someone valuing staying
alive over the perception of "lost time." Once you die, there is
no time to contemplate how much time 90 MPH saved you on Monday!
The truth is that most motorists are essentially ignorant
people in a big mob, hurrying all the time. They do not understand basic
There is no rhyme or reason to it, just
impatience and self-indulgence. But the excuses flow like
Successfully applying risk assessment involves making minor changes to
behavior with the understanding that your overall risk of a tragedy will
greatly reduced. Most people are unable to perform risk assessment because
are unable to look at long-term benefits. Instead they focus on short-term
driving fast gets me there x minutes faster so it must be better.
Unfortunately, there are no hard and fast rules in life. As
this article and the prior article attempt to prove completely opposite
points using the same facts. That is why it is so important to
understand what you learn and not memorize blanket statements and
generalizations. Everything has meaning only in the context to which it
applies. If you continuously seek to educate yourself on everything
around you then you will be in a much stronger position to make
independent decisions based on reason and experience.
Next section ->
Section 3.1 - The Scientific Method