Python

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Reading

books

• Problem Solving with Algorithms and Data Structures Using Python. Release 3.0 by Miller B.N., Ranum D.L. (z-lib.org).pdf

Simulate Probability Problem

# A is guilty, P(A) = 0.01
# B is detected, P(B|A) = 0.8, P(B|~A) = 0.1
# what is P(A|B)

import random

def simulate():
    is_guilty = random.random() < 0.01
    is_detected = random.random() < (0.8 if is_guilty else 0.1)
    return is_guilty, is_detected

n = 1000000
na = 0
nb = 0
nab = 0
for i in range(n):
    is_guilty, is_detected = simulate()
    if is_guilty: na += 1
    if is_detected: nb += 1
    if is_guilty and is_detected: nab += 1
print('P(A) = ', na / n)
print('P(B) = ', nb / n)
print('P(A|B) = ', nab / nb)