# 1763

## Bayes’ theorem

## The book of science

Tom Sharp

Tom Sharp

Thomas Bayes probability |

- Intuition disregards the base rate;
- Bayes taught us to regard it.
- If you think about whether a mammogram
- detects breast cancer,
- you must consider the base rate—
- the prevalence of breast cancer.
- If a mammogram shows
- you have breast cancer
- and the diagnosis is accurate
- only 80 percent of the time
- but only one person in a hundred
- gets breast cancer,
- then your chance of having it is
- only about 7.8 percent.

- Thomas Bayes was lucky in that after he died,
- Richard Price became his literary executor,
- edited his work, wrote an introduction,
- and presented it to the Royal Society.
- Pierre-Simon Laplace developed
- the Bayesian interpretation of probability,
- unaware of the work of Bayes and Price,
- so I might have been writing about Laplace’s theorem.

- Something funny about the human brain,
- might be a throwback to an evolutionary stage
- or a limitation of the structure of its synapses,
- but it needs training from early childhood,
- socializing experiences, help from loved ones,
- continuing stimulation, and constant reminders.

It goes by the name of “logic,” but what we mean is trying to overcome our instinctual thought-processes to adhere more closely to reality.

See also in

The book of science:Probability theory—Blaise Pascal, Pierre de FermatReadings on wikipedia:

Other readings: