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067概率中等derivationshort

Identical Marginals Do Not Imply Independence

题目

Three cards are labeled (0,0)(0,0), (0,1)(0,1), and (1,0)(1,0). One card is drawn uniformly at random. Let XX be the first number and YY the second number on the drawn card. (a) Compute P(X=0)P(X = 0), P(X=1)P(X = 1), P(Y=0)P(Y = 0), and P(Y=1)P(Y = 1). (b) Are the marginal distributions of XX and YY the same? (c) Are XX and YY independent? Verify by checking whether P(X=x,Y=y)=P(X=x)P(Y=y)P(X = x, Y = y) = P(X = x) P(Y = y) holds for all (x,y){0,1}2(x, y) \in \{0,1\}^2.

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你的答案

b

c_independence

P(X=1, Y=1)

P(X=1)P(Y=1)