Question

Exercise 10.4.1: Bayes' Theorem - detecting a biased coin. About (a) Sally has two coins. The first coin is a fair coin and the second coin is biased. The biased coin comes up heads with probability .75 and tails with probability .25. She selects a coin at random and flips the coin ten times. The results of the coin flips are mutually independent. The result of the 10 flips is: T,T,H,T,H,T,T,T,H,T. What is the probability that she selected the biased coin

Answer 1

Answer:

0.026

Step-by-step explanation:

Given the result of 10 coin flips :

T,T,H,T,H,T,T,T,H,T

Number of Heads, H = 3

Number of tails, T = 7

Let :

B = biased coin

B' = non-biased coin

E = event

Probability that it is the biased coin:

P(E Given biased coin) / P(E Given biased coin) * P(E Given non-biased coin) * P(non-biased coin)

P(E|B)P(B) / (P(E|B)*P(B) + P(E|B')P(B')

([(0.75^3) * (0.25^7)] * 0.5) /([(0.75^3) * (0.25^7)] * 0.5) + (0.5^10) * 0.5

0.0000128746 / 0.00050115585

= 0.0263671875