Question

If 7 subjects are selected from the 9 that are​ available, and the 7 selected subjects are all treated at the same​ time, how many different treatment groups are​ possible?

Answer 1

Therefore, we have 36 different treatment groups.

Explanation:

We know that the 7 subjects are selected from the 9 that are​ available, and the 7 selected subjects are all treated at the same​ time.

We calculate how many different treatment groups are​ possible.

We get:

`C_7^9=(9!)/(7!(9-7)!)=(9\cdot 8\cdot 7!)/(7!\cdot 2\cdot 1)= 36`

Therefore, we have 36 different treatment groups.