From a lot of 15 bulbs which include 5 defectives, a sample of 4 bulbs is drawn one by one with replacement. Find the probability distribution of number of defective bulbs. Hence find the mean of the distribution.

Options

A. `1.38`
B. `1.33`
C. `1.39`
D. `1.40`

Answer

B

Explanation

(b) It is given that out of 15 bulbs, 5 are defective.
`:.` Number of non-defective bulb `=15-5=10`
4 bulbs are drawn from a lot with replacement.
Let p=P(drawing defective bulb)`=(5)/(15)=(1)/(3)`
Clearly this is a Bernoulli's trial.
`:'` Mean of Binomial distribution is np
`:. " " 4xx(1)/(3)=1.33" "[`:' n=4, p=(1)/(3)`]`