Suppose three cellphones are tested at random.let D represent the defective cell phone and N represent the non defective cellphone.if we let X be the random variable for the number of defective cellphones,construct the probability distribution of the random variable X

We want to know how many defective telephones there are in the test. The types of results we expect are presented below.

1. In case 1 all three cellphones are defective. $X$ has value 3.
2. In case 2, one cellphone is non defective and two are defective. $X$ has value 2.
3. In case 3, two cellphones are non defective and one is defective. . $X$ has value 1.
4. In case 4, all the three cellphones are non defectives. $X$ has value 0.

The random variable $X$ may take on the values 0,1,2,3

Probability distribution.

$x$ 0 1 2 3

$p(x)$ $P_0$ $P_1$ $P_2$ $P_3$