I created easy explanation of Bayes theorem as a small map: http://immortality-roadmap.com/bayesl.jpg (can't insert jpg into a comment)
It is based on following short story: All men in a port city are either sailors or librarians, and the total male population is 10 000 people, in which are 100 librarians. 80 per cent of the librarians wear glasses, and 9.6 per cent of the sailors wear glasses. If there you meet a man wearing glasses, which is more probable: that he is a librarian or a sailor? The true answer is sailor. The probability that he is librarian results from ratio of two green boxes:
80 / (80 + 950) = 80 / 1030 ≈ 7.8%.
The digits are the same as in original EY explanation, but I exclude the story about mammography, as it may be not easy to understand two complex scientific topics simultaneously. http://www.yudkowsky.net/rational/bayes
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