Reckoning with risk

Reckoning with risk

Learning to live with uncertainty (2002)
By Gerd Gigerenzer

It is rare to read a book nowadays that gives you much thinking and impact after you finished it. I was actually a bit confused, shocked and thinking repeatedly about the contents after I read it. This book is a fairly good one in which you will be able to gain another insight or perspective into uncertainties and life nowadays.

Gerd believes that there should be a curriculum for teaching thinking in an uncertain world. He outlined 3 steps for teaching clear thinking :

1) Recognize types of uncertainties,even those disgused as certainties.
2) Turn uncertainty into risk – measure their degree. Do research to find out more.
3) Teach people to experiment with representations to discover the most transparent way to communicate and reason with risks. Example learning of Bayes’s rule.


…. in this world there is nothing certain but death and taxes. – Benjamin Franklin

People should be aware of Franklins law. The goal is to reduce the illusion of certainty in things. Many people, of varying levels of education, believe that the results of HIV tests, DNA fingerprinting, and the growing number of genetic tests are absolutely certain. These technologies are formidable, but are not foolproof. Like just about everything else, they are subject to Franklin’s law.

If you test HIV positive, what are the chances that you actually have the virus?
Surprisingly, most people even doctors don’t know the answer. The same is true regarding mammography.


Imagine 10,000 men who are not in any known risk category. One is infected (base rate) and will test positive with practical certainty (sensitivity). Of the 9,999 men who are not infected, another one will test positive. (false positive rate).

The author tells that if diagnosed with a major illness such as cancer or HIV, you should get a second opinion or a third. Never trust a single test. Ever.

Gred tells the story of a construction worker who has always been tested negative for HIV, does in fact have been infected with the HIV virus. Furthermore, as his medical examination of HIV virus has always been tested negative, he had in good faith donated blood more than 30 times in the previous 4 years. In each case, the routine ELISA- which is used to screen all blood donations for the HIV virus – returned a negative result. The consequences for those who received the construction worker’s blood are unknown. This HIV-infected man had tested negative for HIV no fewer than 35 times over a four year period.

A case like the above is very rare; nevertheless, it could happen again. Perhaps it goes to show that like just about everything else, it is subjected to Franklin’s law.

…. in this world there is nothing certain but death and taxes. – Benjamin Franklin



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