Re: 20 Greatest Beatles songs


"Sean Carroll" <seanc130@xxxxxxxxxxx> wrote in message
news:ou8Bi.230878$dA7.89368@xxxxxxxxxxxxxxx
poisoned rose wrote:
Sean Carroll <seanc130@xxxxxxxxxxx> wrote:

That's correct. The number of combinations (order doesn't matter) of n
things taken j at a time is n! / [(n - j)!j!]. If you're doing
permutations (order matters), then it's n! / (n - j)!.

Yeah...that's what I was a bit fuzzy about. The difference between the
"order matters" and "order doesn't matter" computations.

Just remember that, since there are fewer combinations (order doesn't
matter) than there are permutations (order does matter), it's a smaller
number. Thus, you divide the permutations formula by an extra j! to get
the combinations formula.


There are more combinations than permutations, that's why you get a smaller
number. The chances of having a combination turn up are greater than the
chances of having a specific permutation come up.



.

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