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Paper 4 (9164, Section A) · November 2009 · Expectation of a linear function

A random variable X has E(X) = 10 and Var(X) = 9. Find E(Y) where Y = 2X - 3.

Model answer

17

Also accepted: 17.0, 17,0

Explanation

For constants a and b, $E(aX+b)=aE(X)+b$ .

$E(Y)=E(2X-3)=2E(X)-3=2(10)-3=20-3=17$ .

Derived from ZIMSEC Statistics Paper 4, November 2009, Q1

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