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Random Variables, Expectation & Variance · Question 40 of 68

Question 40

MediumOriginal question

$E(X) = 3$ . What is $E(2X + 5)$ ?

6

Correct answerYour answer

8

Correct answerYour answer

11

Correct answerYour answer

16

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

Expectation is linear: $E(aX + b) = aE(X) + b$ .
$E(2X + 5) = 2 \times 3 + 5 = 11$ .

Worth noting

6 doubles the mean but drops the $+5$ .

Concept: The expectation of aX + b
Typical timeTypical: 90 s
Your timeYours: —

The rule this testsMathematical expectation

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