Question

Let D represent the defective cell phone and N represents the non – defective cell phone. If we let X be the random variable representing the number of defective if three cell phones are tested at random, show the values of the random variable X?

Answer 1

If three cell phones are tested there are four possible outcomes:

1. All three are working and none is defective and thus X is 0
2. One phone is defective and the other two are working and thus X is 1
3. Two phones are defective and only one is working and thus X is 2
4. All three phones are defective and thus X is 3

The probability distribution of X is thus: