Question

A group of four IC chips consists of two good chips and two defective chips. The experiment consists of selecting three chips at random from this group. Write the sample space of the possible outcomes. What is the probability that two are defective?

Answer 1

Let $D$ denote the event "defective chip", let $G$ denote the event "good chip".

The sample space of the possible outcomes is

$$S=\{GGD, GDG, GDD, DGG, DGD, DDG\}$$

$$P(2\ defective)=\dfrac{3}{6}=\dfrac{1}{2}$$