In a binomial distribution, the probability of getting a success is $\frac{1}{3}$ and the standard deviation is 2. Then its mean is :
Answer & explanation
Correct answer: option 4
$p=\frac{1}{3},\;q=\frac{2}{3}.$
$\text{Standard deviation }=\sqrt{npq}=2.$
$npq=4.$
$n\cdot\frac{2}{9}=4.$
$n=18.$
$\text{Mean }=np=18\cdot\frac{1}{3}=6.$
$\text{Mean }=6.$