40% of the customers that come into a discount store purchases something. Find the probability that 3 of the next 5 customers make a purchase. (binomial random variable)
(p) = 5!
---------------(.4)to the 3rd (.6) to 5-3
3!(5-2)!
5!
----------(.4)to the 3rd (.6) to the 2nd---
3!2!
5*4*3*2*1
------------(.4)to the 3rd (.6)tothe 2nd
(3*2*1)(2*1)
=10(.064)(.36)
=.2304
My question is how do they come up with (3*2*1)(2*1) of the problem, I do not know how they come up with this, and was hoping that I could get it explained to me so I can work on some of my problems.
Thanks.
(p) = 5!
---------------(.4)to the 3rd (.6) to 5-3
3!(5-2)!
5!
----------(.4)to the 3rd (.6) to the 2nd---
3!2!
5*4*3*2*1
------------(.4)to the 3rd (.6)tothe 2nd
(3*2*1)(2*1)
=10(.064)(.36)
=.2304
My question is how do they come up with (3*2*1)(2*1) of the problem, I do not know how they come up with this, and was hoping that I could get it explained to me so I can work on some of my problems.
Thanks.