Question

A symmetrical die is thrown four times and getting
a multiple of 2 is considered to be a success.
The mean and variance of success are

• A. $4,2$
• B. $2,1$
• C. $0,2$
• D. $1,2$

Answer 1

Answer: (B)

$2,1$

The probability of getting a multiple of 2 for one throw is $\frac{3}{6}$
$=\frac{1}{2}$
Hence the mean will be
$np$
$=4\left(\frac{1}{2}\right)$
$=2$

Now the variance will be
$np(1-p)$

$=2(1-\frac{1}{2})$
$=1$