00:01
So a salesman normally makes a sale where he closes the deal to be 60%.
00:11
We'll say that's 0 .6.
00:12
Assuming the presentations are independent, find the probability of each of the following.
00:18
So part a, we want the probability that he fails to close for the first time on his fourth attempt.
00:26
So that meant he closed, then he closed, then he closed.
00:32
Then he closed, and his first failure was on the fourth attempt.
00:38
So the probability of him closing is 0 .6 times 0 .6 times 0 .6.
00:46
And then he fails.
00:48
Well, if he closes 60 % of the time, then he fails, then he fails 40 % of the time.
00:54
And if you multiply those all out, you will get 0 .0864.
01:00
Now, this is a geometric probability and to do the geometric probability we are talking about the probability of the first success to be defined by the probability of success times the probability of failure to the n minus one power so in this part a we are talking about the first failure on the fourth so the probability of the first failure on the fourth? well, the probability of failure is 0 .4, and the probability of not failing or closing was 0 .6.
01:41
And then we'd have 4 minus 1 power, and that's going to get us the same value.
01:48
Now, rather than me using x here, i could use n here.
01:55
So we can do it either of the two ways.
01:57
For part b, we want the probability that he closes his first presentation on his third attempt.
02:07
So that means he failed on the first, he failed on the second, and closed on the third.
02:14
So failure is 40 % of the time and closing is 60 % of the time.
02:20
And if we multiply that out, we would get 0 .096...