CA Foundation · Quantitative Aptitude · Probability
Two independent random variables X and Y have E(X) = 12 and E(Y) = 5. What is E(XY)?
E(XY) equals 60. When two random variables are independent, the expectation of their product is the product of their expectations, so 12 multiplied by 5 gives 60. The figure 17 is the expectation of the sum, not the product.
- A17
- B7
- C60Correct
- D2.4
Explanation
For independent variables, E(XY) = E(X)E(Y) = 12 x 5 = 60. The value 17 is E(X+Y), which is a different quantity, and 7 is E(X) - E(Y).
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