Question

Let $X$ be discrete random variable. The probability distribution of $X$ is given below.

$X$	30	10	-10
$P(X)$	$\frac{1}{5}$	$\frac{3}{10}$	$\frac{1}{2}$

Then, $E(X)$ is equal to

• A. 6
• B. 4
• C. 3
• D. $-5$

Answer 1

Answer: (B)

Given that

$X$	30	10	-10
$P(X)$	$\frac{1}{5}$	$\frac{3}{10}$	$\frac{1}{2}$

$E(X)=30\times \frac{1}{5}+10\times \frac{3}{10}+(-10)\times \frac{1}{2}$
$=6+3-5=9-5$
$=4$