Question

A firm manufactures light bulbs and those that come out of the assembly line are either defective or good. Every five bulbs that come out, 1 is defective. If 3 bulbs are selected at random, what is the probability that:

(i) All 3 are defective
(ii) All 3 are good
(iii) The first selected is defective
(iv) 1 defective and 2 good
(v) 2 defective and 1 good
(vi) At most 2 are good

Answer 1

If the events are independent, the probability of both/all events occurring is determined by multiplying the probabilities of the individual events.

1. (1/5)^3 = ?

2. (4/5)^3 = ?

3. 1/5

4. 1/5 * 4/5 * 4/5 = ?

5. You do it, using similar process.

6. This is none good, one good <I>or</I> 2 good.

Either-or probabilities are found by adding the individual probabilities.