00:01
So in this question, we have some survey data, and we now pick 20 randomly selected drivers.
00:08
So n is going to be 20.
00:10
And the probability that they cut recreational driving, i'll call this a, is 30%, so 0 .3.
00:22
The probability they say it was consolidating or reducing errands, i'll call this b, is 27%.
00:30
So, looking at this, we have 20 independent trials, and we have some possible outcomes.
00:40
Now, for part a, we want the probability that's exactly eight, said it was because of b, errant.
00:48
But they cut back on their errands.
00:51
So i can just kind of ignore a.
00:53
I'm going to just lump it in with not reducing errands.
00:58
So they gave a reason other than this.
01:01
I can say i have a binomial distribution.
01:04
20 independent trials, two outcomes, either part of this 27 % or not, same probability for each person.
01:13
Great.
01:14
So i can use the binomial function to solve this.
01:17
You could use the binomial formula.
01:19
You could use your graphical calculator.
01:22
You could use software like excel or r.
01:24
I'm going to use excel.
01:25
The function is binom .disk, and there are four arguments to insert here.
01:33
They are.
01:34
X, the number who agree with this.
01:37
N, number of trials.
01:39
P probability of success.
01:41
And whether or not i want the cumulative probability or not.
01:46
So here i want exactly eight.
01:49
So if i put that into the function, that would be 8 .20.
01:53
The probability of them agreeing with this is 0 .27.
01:57
And false...