00:01
Okay, so let's talk about the difference between a combination or a permutation.
00:04
In a combination, order does not matter.
00:08
So if i were to select events a, b, and c, this is the same as selecting events b, and c.
00:13
All that matters is that you were selected.
00:16
Whereas a permutation, this is saying that order does matter.
00:23
So then selecting events a, b, and c is different than selecting events b and c.
00:28
So here, a researcher wishes her patients to try new medicine.
00:32
She wants to select five from 50.
00:34
Does the order matter? order does not matter, so this is a combination, 50, choose five.
00:40
This will be approximately the first number factorial over the bottom number factorial, over subtract those two numbers factorial, which is 45 factorial.
00:49
So expanding this out a little bit, this will be 50 times 49, times 48, times 47, times 46 times 40 into 45 factorial, all over 45 factorial, which will cancel...