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Questions › DSE › DSE 2011 › Q31
2 marksStatistics › Joint distributions, covariance and correlation › Joint, marginal and conditional distributionsModerateabout 3 min

DSE 2011 Question 31: Joint distributions, covariance and correlation

Suppose XXX and YYY are random variables. XXX takes values −1-1−1 and 111; YYY takes integer values 1 to 6. The joint distribution has P(X=−1)P(X=-1)P(X=−1) row [0.1, a, 0.3, 0, 0, 0][0.1,\ a,\ 0.3,\ 0,\ 0,\ 0][0.1, a, 0.3, 0, 0, 0] and P(X=1)P(X=1)P(X=1) row [0, 0, b, 0.1, 0.1, 0.1][0,\ 0,\ b,\ 0.1,\ 0.1,\ 0.1][0, 0, b, 0.1, 0.1, 0.1] across Y=1,…,6Y=1,\ldots,6Y=1,…,6. It is known that E(X)=−0.2E(X)=-0.2E(X)=−0.2 and E(Y)=3.2E(Y)=3.2E(Y)=3.2. The value 'aaa' in the table equals

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Suppose X and Y are random variables. X takes values -1 and 1; Y takes integer values 1 to 6. The joint distribution has P(X=-1) row [0.1, a, 0.3, 0, 0, 0] and P(X=1) row [0, 0, b, 0.1, 0.1, 0.1] across Y=1,…,6. It is known that E(X)=-0.2 and E(Y)=3.2. The value ' a ' in the table equals (A) 0 (B) 0.1 (C) 0.2 (D) 0.3

Also written as: Suppose X and Y are random variables. X takes values -1 and 1; Y takes integer values 1 to 6. The joint distribution has P(X=-1) row [0.1, a, 0.3, 0, 0, 0] and P(X=1) row [0, 0, b, 0.1, 0.1, 0.1] across Y=1,...,6. It is known that E(X)=-0.2 and E(Y)=3.2. The value ' a ' in the table equals

Joint distributions, covariance and correlation has come up 61 times in 7 exams since 2005.

What this question tests

This question is on Joint, marginal and conditional distributions, part of Joint distributions, covariance and correlation in Statistics.

How two random variables behave together and separately.

TestStop has 14 past-paper questions on this subtopic.

Practise Joint distributions, covariance and correlationMore on Joint, marginal and conditional distributions

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