Outreach in Computer Science
Bayesian solutions to real-world risk problems
Did the Doctor
make the correct medical diagnosis?
Consider the following
in a thousand people has a prevalence for a particular heart disease.
There is a test to detect this disease. The test is 100%
for people who have the disease and is 95% accurate for those who don't
(this means that 5% of people who do not have the disease will be
wrongly diagnosed as having it).
If a randomly selected person tests positive what is the probability
that the person actually has the disease?"
This question was put to
60 students and staff at Harvard Medical School.
Almost half gave the
The 'average' answer was
In fact, the correct
answer is very different and was given by just
for the answer and an explanation.
Return to Main Page
Making Sense of Probability: Fallacies, Myths and Puzzles