Brain Teaser The Reverend Thomas Bayes (1702–

1761) was an English mathematician who discovered an important rule of probability (see Bayes’s theorem, Appendix I, part I). A key feature of Bayes’s theorem is the formula P(B) 5P(B | A) ? P(A) 1P(B | Ac ) ? P(Ac )

Explain why this formula is valid. Hint: See Figure Al-1 in Appendix I.

AppendixLO1