Three defective bulbs are mixed with 8 good ones. If three bulbs are drawn one by one with replacement, the probabilities of getting exactly 1 defective, more than 2 defective, no defective and more than 1 defective respectively are: |
$\frac{27}{1331}, \frac{576}{1331}, \frac{243}{1331}$ and $\frac{512}{1331}$ $\frac{27}{1331}, \frac{243}{1331}, \frac{576}{1331}$ and $\frac{512}{1331}$ $\frac{576}{1331}, \frac{27}{1331}, \frac{512}{1331}$ and $\frac{243}{1331}$ $\frac{243}{1331}, \frac{576}{1331}, \frac{512}{1331}$ and $\frac{27}{1331}$ |
$\frac{576}{1331}, \frac{27}{1331}, \frac{512}{1331}$ and $\frac{243}{1331}$ |
The correct answer is Option (3) → $\frac{576}{1331}, \frac{27}{1331}, \frac{512}{1331}$ and $\frac{243}{1331}$ Total bulbs $=11$, defective $=3$, good $=8$ Probability of defective $p=\frac{3}{11}$, good $q=\frac{8}{11}$ Three draws with replacement ⇒ binomial with $n=3$ Probability of exactly $1$ defective $P(X=1)=\frac{3!}{1!2!}p q^2 =3\cdot\frac{3}{11}\cdot\left(\frac{8}{11}\right)^2 =\frac{576}{1331}$ Probability of more than $2$ defective means $X=3$ $P(X=3)=p^3=\left(\frac{3}{11}\right)^3=\frac{27}{1331}$ Probability of no defective $P(X=0)=q^3=\left(\frac{8}{11}\right)^3=\frac{512}{1331}$ Probability of more than $1$ defective means $X=2$ or $3$ $P(X\ge2)=P(X=2)+P(X=3)$ $P(X=2)=\frac{3!}{2!1!}p^2 q =3\cdot\left(\frac{3}{11}\right)^2\cdot\frac{8}{11} =\frac{216}{1331}$ $P(X\ge2)=\frac{216}{1331}+\frac{27}{1331}=\frac{243}{1331}$ The required probabilities are Exactly $1$ defective $=\frac{576}{1331}$, More than $2$ defective $=\frac{27}{1331}$, No defective $=\frac{512}{1331}$, More than $1$ defective $=\frac{243}{1331}$. |