### 2022 Q1(1)   2024.7.26

import numpy as np

# シミュレーションの回数
num_simulations = 1000000

# 与えられた確率
prob = 3/4

# 事象 A, B, C をシミュレーション
A = np.random.rand(num_simulations) < prob
B = np.random.rand(num_simulations) < prob
C = np.random.rand(num_simulations) < prob

# 交差確率の計算
P_A_and_B = np.mean(A & B)
P_A_and_B_and_C = np.mean(A & B & C)

P_A_and_B, P_A_and_B_and_C

(0.56311, 0.422594)

#検算
9/16,27/64

(0.5625, 0.421875)

### 2022 Q1(2)   2024.7.26

import numpy as np

def simulate_overlap_with_fixed_true(correlation):
    P_A = 3/4
    P_B = 3/4
    num_elements = 1000
    num_true_A = int(P_A * num_elements)
    num_true_B = int(P_B * num_elements)

    # A と B の配列を生成し、3/4がtrueになるように設定
    A = np.zeros(num_elements, dtype=bool)
    A[:num_true_A] = True
    np.random.shuffle(A)

    B = np.zeros(num_elements, dtype=bool)
    B[:num_true_B] = True
    np.random.shuffle(B)

    if correlation == 'positive':
        # 正の相関を持たせるために、スワップを行う
        A1_B0_indices = np.where(A & ~B)[0]
        A0_B1_indices = np.where(~A & B)[0]

        min_len = min(len(A1_B0_indices), len(A0_B1_indices))
        for i in range(min_len):
            B[A1_B0_indices[i]], B[A0_B1_indices[i]] = B[A0_B1_indices[i]], B[A1_B0_indices[i]]

    elif correlation == 'negative':
        # 負の相関を持たせるために、スワップを行う
        A1_B1_indices = np.where(A & B)[0]
        A0_B0_indices = np.where(~A & ~B)[0]

        min_len = min(len(A1_B1_indices), len(A0_B0_indices))
        for i in range(min_len):
            B[A1_B1_indices[i]], B[A0_B0_indices[i]] = B[A0_B0_indices[i]], B[A1_B1_indices[i]]

    else:
        raise ValueError("Invalid correlation type")

    # 重なりの割合を計算
    overlap_ratio = np.mean(A & B)

    return overlap_ratio

# 正の相関の場合
overlap_positive = simulate_overlap_with_fixed_true('positive')

# 負の相関の場合
overlap_negative = simulate_overlap_with_fixed_true('negative')

overlap_positive, overlap_negative

(0.75, 0.5)