Exercise 2.58

Answers

(a)
If A and B are independent, then P(A|B,C) = P(A|Bc,C) = P(A|C).

P(A|B,Cc) = P(A|Bc,Cc) = P(A|Cc).

Thus, Simpson’s Paradox does not hold.

(b)
If A and C are independent, then P(A|B,C) < P(A|Bc,C)P(A|B) < P(A|Bc). Thus, Simpson’s Paradox does not hold.
(c)
If B and C are independent, then P(A|B) = P(C)P(A|B,C) + P(Cc)P(A|B,Cc).

P(A|Bc) = P(C)P(A|Bc,C) + P(Cc)P(A|Bc,Cc).

Since P(A|B,C) > P(A|Bc,C) and P(A|B,Cc) > P(A|Bc,Cc), P(A|B) > P(A|Bc), so Simpson’s Paradox does not hold.

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2021-12-05 00:00
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