Question

In an experiment involving a treatment applied to 5 test subjects, researchers plan to use a simple random sample of 5 subjects selected from a pool of 7 available subjects. How many different random samples are possible?

Answer 1

The number of ways to select 5 from 7 (when order does not matter) is;

`\begin{gathered} ^7C_5=(7!)/((7-5)!5!) \\ \\ ^7C_5=(7*6*5!)/(2!*5!) \\ \\ ^7C_5=21 \end{gathered}`

ANSWER: 21 ways