Answer:
Therefore, we have 36 different treatment groups.
Step-by-step 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:
[tex]C_7^9=\frac{9!}{7!(9-7)!}=\frac{9\cdot 8\cdot 7!}{7!\cdot 2\cdot 1}= 36[/tex]
Therefore, we have 36 different treatment groups.
