Suppose there are 10 students in your class. You want to select three out of them. How many samples are possible?

Population = 10
$$\begin{gathered} \mathrm{Number} \mathrm{of} \mathrm{possible} \mathrm{samples}={}^{n}C_r={}^{10}C_3 \\ =\frac{10!}{3! \left(10-3\right)!} \\ =\frac{10!}{3! 7!} \\ = 120 \end{gathered}$$

Thus, 120 samples are possible in the above scenario.