statictics

Question

an inspector must select three tests to perform in a certain order on a manufactured part.He has a choice of 9 tests.How many ways can he perform 3 differnt tests?

Answer 1

Tiffany,

 

        The number of ways to choose 3 out of nine with regard to the order of the three tests is ₉P₃=9!/((9-3)!)=504.

 

If the tests are numbered 1 2 3....7 8 9 a sample of size 3 might be 1 3 2 or 3 2 1 these 2 combinations would be counted as 2 tests because the order is different

 

Hope this helps

 

Jim

Answer 2

I believe that this questions states the tests must be performed IN A CERTAIN ORDER.  That's the clue that ORDER MATTERS, so this is a PERMUTATION problem rather than being a COMBINATION problem.

 

So the correct answer is 9P3 = 9 factorial divided by (9-3) factorial = 9(8)(7).

Answer 3

Tiffany

 

You have 9 options and need to choose 3

 

₉C₃ = 9!/[(3!)(9-3)!]

 

9!/[3!6!]

 

9•8•7     

-------  =   84  

3•2•1