gmatt1476 wrote:
A box of light bulbs contains exactly 3 light bulbs that are defective. What is the probability that a sample of light bulbs picked at random from this box will contain at least 1 defective light bulb?
(1) The light bulbs in the sample will be picked 1 at a time without replacement.
(2) The sample will contain exactly 20 light bulbs.
DS76851.01
Question stem- No.of defective light bulbs are 3.
Total no.of bulbs= unknown
We are asked to find -the probability that a sample of light bulbs picked at random from this box will contain at least 1 defective light bulb.
We need to know total no.of bulbs present in the box and picking methods.
statement 1- Insufficient
Total no.of bulbs not known
Statement 2-insufficient
Picking method not known. We don't know whether 1 bulb is picked at a time, 2 picked at a time or with/without replacement.
.
Statement 1 + Statement 2
Insufficient.
Reason is we cannot arrive at a unique answer because question stem asks to find probability that atleast 1 defective bulb is picked.
There are 3 cases possible here-
one is defective, 2 defective, 3 are defective. The probability of these 3 cases gives different answer. Hence correct option is E.
_________________