00:01
So there are 23 available people.
00:04
The pollster is going to pick four of them.
00:06
We want to know how many ways that could happen.
00:09
Okay, so we're going to be picking people without repetition.
00:12
The same person won't be surveyed multiple times.
00:16
And the order in which they are selected doesn't matter.
00:20
We just want to know which ones are going to be surveyed.
00:24
With those two rules in mind, this is a combinations question.
00:29
The formula for combinations, n, choose r is n factorial over r factorial n minus r factorial.
00:37
So we want 23 choose 4.
00:40
The number of ways to pick 4 from a group of 23 without repetition where the order doesn't matter.
00:46
23 factorial over 4 factorial, 19 factorial.
00:52
And that is 8 ,855.
00:57
What's the probability a particular person would be a member of this group? okay, so i'll show you a very simple way, and then a more complicated way.
01:06
The simple way is he's picking four out of 23...