Question

In a binomial distribution mean is $5$, and variance $4$, then the number of trials is

• A. $100$
• B. $50$
• C. $25$
• D. $24$

Answer 1

Answer: (C)

$25$

$Mean=np=5$
$Variance=np(1-p)=4$
$\Rightarrow np(1-p)=4$
$\Rightarrow 5(1-p)=4$
$\Rightarrow 1-p=\frac{4}{5}$

$\therefore p=\frac{1}{5}$

Hence, no.of trials (n) will be
$=\frac{5}{p}$
$=5\left(5\right)$
$=25$