Using the binomial distribution, we have that:
a) 0.1024 = 10.24% probability that the marketing representative must select 4 people to find one who attended the last home football game.
b) 0.2621 = 26.21% probability that the marketing representative must select more than 6 people to find one who attended the last home football game.
c) The expected number of people is 4, with a variance of 20.
For each person, there are only two possible outcomes. Either they attended a game, or they did not. The probability of a person attending a game is independent of any other person, which means that the binomial distribution is used.
Binomial probability distribution
The parameters are:
- p is the probability of a success on a single trial.
- n is the number of trials.
- p is the probability of a success on a single trial.
The expected number of <u>trials before q successes</u> is given by:
![E = \frac{q(1-p)}{p}](https://tex.z-dn.net/?f=E%20%3D%20%5Cfrac%7Bq%281-p%29%7D%7Bp%7D)
The variance is:
![V = \frac{q(1-p)}{p^2}](https://tex.z-dn.net/?f=V%20%3D%20%5Cfrac%7Bq%281-p%29%7D%7Bp%5E2%7D)
In this problem, 0.2 probability of a finding a person who attended the last football game, thus
.
Item a:
- None of the first three attended, which is P(X = 0) when n = 3.
- Fourth attended, with 0.2 probability.
Thus:
![P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}](https://tex.z-dn.net/?f=P%28X%20%3D%20x%29%20%3D%20C_%7Bn%2Cx%7D.p%5E%7Bx%7D.%281-p%29%5E%7Bn-x%7D)
![P(X = 0) = C_{3,0}.(0.2)^{0}.(0.8)^{3} = 0.512](https://tex.z-dn.net/?f=P%28X%20%3D%200%29%20%3D%20C_%7B3%2C0%7D.%280.2%29%5E%7B0%7D.%280.8%29%5E%7B3%7D%20%3D%200.512)
![0.2(0.512) = 0.1024](https://tex.z-dn.net/?f=0.2%280.512%29%20%3D%200.1024)
0.1024 = 10.24% probability that the marketing representative must select 4 people to find one who attended the last home football game.
Item b:
This is the probability that none of the first six went, which is P(X = 0) when n = 6.
![P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}](https://tex.z-dn.net/?f=P%28X%20%3D%20x%29%20%3D%20C_%7Bn%2Cx%7D.p%5E%7Bx%7D.%281-p%29%5E%7Bn-x%7D)
![P(X = 0) = C_{6,0}.(0.2)^{0}.(0.8)^{6} = 0.2621](https://tex.z-dn.net/?f=P%28X%20%3D%200%29%20%3D%20C_%7B6%2C0%7D.%280.2%29%5E%7B0%7D.%280.8%29%5E%7B6%7D%20%3D%200.2621)
0.2621 = 26.21% probability that the marketing representative must select more than 6 people to find one who attended the last home football game.
Item c:
- One person, thus
.
The expected value is:
![E = \frac{q(1-p)}{p} = \frac{0.8}{0.2} = 4](https://tex.z-dn.net/?f=E%20%3D%20%5Cfrac%7Bq%281-p%29%7D%7Bp%7D%20%3D%20%5Cfrac%7B0.8%7D%7B0.2%7D%20%3D%204)
The variance is:
![V = \frac{0.8}{0.04} = 20](https://tex.z-dn.net/?f=V%20%3D%20%5Cfrac%7B0.8%7D%7B0.04%7D%20%3D%2020)
The expected number of people is 4, with a variance of 20.
A similar problem is given at brainly.com/question/24756209