If the mean and standard deviation of a binomial variate X are 8 and 2 respectively, then P(X≥1) is :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $1-\frac{1}{2^{16}}$
In Binomial Distribution,
Mean, $μ=np=8$ ....(1)
Standard Deviation, $σ=\sqrt{np(1-p)}=2$ ....(2)
from (1) and (2) we get,
$np(1-p)=2$
$⇒8(1-p)=2$
$⇒p=\frac{1}{2}$
$⇒n=\frac{8}{p}=16$
$∴P(X≥1)=1-P(X=0)$
$=1-{^{16}C}_0(\frac{1}{2})^0(\frac{1}{2})^{16}$
$=1-\frac{1}{2^{16}}$