00:01
So 25 % of people say that they like to have their pets bathed professionally.
00:08
If we took a random sample of 18 people, what is the probability that of those 18 people, exactly five of them would get their pets bathed professionally.
00:29
So let's take a look at what this binomial distribution the probability of a binomial distribution formula is.
00:38
We're going to do n factorial over n minus x factorial times x factorial, multiply that times p to the x, times one minus p to the n minus x.
00:59
So let's take a look.
01:01
So n is 18.
01:04
So we're going to do 18 factorial.
01:06
Our x is 5 that's this value here so 18 minus 5 is 13 factorial times 5 factorial our p is 0 .25 to the 5 power and 1 minus 0 .25 to the n minus x which is 13 18 factorial divided by 13 factorial times 5 factorial is 8 ,568.
01:47
Remember, this 18 factorial means 18 times 17 times 16 times 15 all the way up to 1, and then 13 factorial is the same, and then 5 is from 1 to 5.
01:59
You could also find this factorial button in your calculator by clicking math and going over to prb, and you'll see it on the list...