Var(X) = 3. What is Var(2X + 7)?

Random Variables, Expectation & Variance · Question 55 of 68

Question 55

EasyOriginal question

$\text{Var}(X) = 3$ . What is $\text{Var}(2X + 7)$ ?

6

Correct answerYour answer

11

Correct answerYour answer

12

Correct answerYour answer

13

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

$\text{Var}(aX + b) = a^{2}\,\text{Var}(X)$ : the constant $b$ does not spread the values.
$2^{2} \times 3 = 12$ .

Worth noting

6 multiplies by 2 instead of $2^{2}$ ; 13 adds 7 as well, which is wrong too.

Ten questions from Random Variables, Expectation & Variance, at your own pace.

Ten questions from Random Variables, Expectation & Variance, at your own pace.