Answer:
(a) P (X = 6) = 0.12214, P (X ≥ 6) = 0.8088, P (X ≥ 10) = 0.2834.
(b) The expected value of the number of small aircraft that arrive during a 90-min period is 12 and standard deviation is 3.464.
(c) P (X ≥ 20) = 0.5298 and P (X ≤ 10) = 0.0108.
Step-by-step explanation:
Let the random variable <em>X</em> = number of aircraft arrive at a certain airport during 1-hour period.
The arrival rate is, <em>λ</em>t = 8 per hour.
(a)
For <em>t</em> = 1 the average number of aircraft arrival is:
![\lambda t=8\times 1=8](https://tex.z-dn.net/?f=%5Clambda%20t%3D8%5Ctimes%201%3D8)
The probability distribution of a Poisson distribution is:
![P(X=x)=\frac{e^{-8}(8)^{x}}{x!}](https://tex.z-dn.net/?f=P%28X%3Dx%29%3D%5Cfrac%7Be%5E%7B-8%7D%288%29%5E%7Bx%7D%7D%7Bx%21%7D)
Compute the value of P (X = 6) as follows:
![P(X=6)=\frac{e^{-8}(8)^{6}}{6!}\\=\frac{0.00034\times262144}{720}\\ =0.12214](https://tex.z-dn.net/?f=P%28X%3D6%29%3D%5Cfrac%7Be%5E%7B-8%7D%288%29%5E%7B6%7D%7D%7B6%21%7D%5C%5C%3D%5Cfrac%7B0.00034%5Ctimes262144%7D%7B720%7D%5C%5C%20%3D0.12214)
Thus, the probability that exactly 6 small aircraft arrive during a 1-hour period is 0.12214.
Compute the value of P (X ≥ 6) as follows:
![P(X\geq 6)=1-P(X](https://tex.z-dn.net/?f=P%28X%5Cgeq%206%29%3D1-P%28X%3C6%29%5C%5C%3D1-%5Csum%5Climits%5E%7B5%7D_%7Bx%3D0%7D%28%5Cfrac%7Be%5E%7B-8%7D%288%29%5E%7Bx%7D%7D%7Bx%21%7D%29%5C%5C%3D1-0.19123%5C%5C%3D0.80877%5C%5C%5Capprox0.8088)
Thus, the probability that at least 6 small aircraft arrive during a 1-hour period is 0.8088.
Compute the value of P (X ≥ 10) as follows:
![P(X\geq 10)=1-P(X](https://tex.z-dn.net/?f=P%28X%5Cgeq%2010%29%3D1-P%28X%3C10%29%5C%5C%3D1-%5Csum%5Climits%5E%7B9%7D_%7Bx%3D0%7D%28%5Cfrac%7Be%5E%7B-8%7D%288%29%5E%7Bx%7D%7D%7Bx%21%7D%29%5C%5C%3D1-0.71663%5C%5C%3D0.28337%5Capprox0.2834)
Thus, the probability that at least 10 small aircraft arrive during a 1-hour period is 0.2834.
(b)
For <em>t</em> = 90 minutes = 1.5 hour, the value of <em>λ</em>, the average number of aircraft arrival is:
![\lambda t=8\times 1.5=12](https://tex.z-dn.net/?f=%5Clambda%20t%3D8%5Ctimes%201.5%3D12)
The expected value of the number of small aircraft that arrive during a 90-min period is 12.
The standard deviation is:
![SD=\sqrt{\lambda t}=\sqrt{12}=3.464](https://tex.z-dn.net/?f=SD%3D%5Csqrt%7B%5Clambda%20t%7D%3D%5Csqrt%7B12%7D%3D3.464)
The standard deviation of the number of small aircraft that arrive during a 90-min period is 3.464.
(c)
For <em>t</em> = 2.5 the value of <em>λ</em>, the average number of aircraft arrival is:
![\lambda t=8\times 2.5=20](https://tex.z-dn.net/?f=%5Clambda%20t%3D8%5Ctimes%202.5%3D20)
Compute the value of P (X ≥ 20) as follows:
![P(X\geq 20)=1-P(X](https://tex.z-dn.net/?f=P%28X%5Cgeq%2020%29%3D1-P%28X%3C20%29%5C%5C%3D1-%5Csum%5Climits%5E%7B19%7D_%7Bx%3D0%7D%28%5Cfrac%7Be%5E%7B-20%7D%2820%29%5E%7Bx%7D%7D%7Bx%21%7D%29%5C%5C%3D1-0.47025%5C%5C%3D0.52975%5C%5C%5Capprox0.5298)
Thus, the probability that at least 20 small aircraft arrive during a 2.5-hour period is 0.5298.
Compute the value of P (X ≤ 10) as follows:
![P(X\leq 10)=\sum\limits^{10}_{x=0}(\frac{e^{-20}(20)^{x}}{x!})\\=0.01081\\\approx0.0108](https://tex.z-dn.net/?f=P%28X%5Cleq%2010%29%3D%5Csum%5Climits%5E%7B10%7D_%7Bx%3D0%7D%28%5Cfrac%7Be%5E%7B-20%7D%2820%29%5E%7Bx%7D%7D%7Bx%21%7D%29%5C%5C%3D0.01081%5C%5C%5Capprox0.0108)
Thus, the probability that at most 10 small aircraft arrive during a 2.5-hour period is 0.0108.