Question

From a box containing 4 defective and 5 non defective items,

how many samples of size 3 are possible?

Answer 1

The box contains both defective and non defective items. Let $D$ be the event that an item is defective and $D'$ be the event that an item is non defective. Therefore, there are $k=2$ sets of events. If samples of size $n=3$ are drawn from this box then, we expect $k^n$ possible samples. Therefore, the number of possible samples are, $k^n=2^3=8$.