Answer:
Part a: <em>The probability of no arrivals in a one-minute period is 0.000045.</em>
Part b: <em>The probability of three or fewer passengers arrive in a one-minute period is 0.0103.</em>
Part c: <em>The probability of no arrivals in a 15-second is 0.0821.</em>
Part d: <em>The probability of at least one arrival in a 15-second period is 0.9179.</em>
Step-by-step explanation:
Airline passengers are arriving at an airport independently. The mean arrival rate is 10 passengers per minute. Consider the random variable X to represent the number of passengers arriving per minute. The random variable X follows a Poisson distribution. That is,
![X \sim {\rm{Poisson}}\left( {\lambda = 10} \right)](https://tex.z-dn.net/?f=X%20%5Csim%20%7B%5Crm%7BPoisson%7D%7D%5Cleft%28%20%7B%5Clambda%20%3D%2010%7D%20%5Cright%29)
The probability mass function of X can be written as,
![P\left( {X = x} \right) = \frac{{{e^{ - \lambda }}{\lambda ^x}}}{{x!}};x = 0,1,2, \ldots](https://tex.z-dn.net/?f=P%5Cleft%28%20%7BX%20%3D%20x%7D%20%5Cright%29%20%3D%20%5Cfrac%7B%7B%7Be%5E%7B%20-%20%5Clambda%20%7D%7D%7B%5Clambda%20%5Ex%7D%7D%7D%7B%7Bx%21%7D%7D%3Bx%20%3D%200%2C1%2C2%2C%20%5Cldots)
Substitute the value of λ=10 in the formula as,
![P\left( {X = x} \right) = \frac{{{e^{ - \lambda }}{{\left( {10} \right)}^x}}}{{x!}}](https://tex.z-dn.net/?f=P%5Cleft%28%20%7BX%20%3D%20x%7D%20%5Cright%29%20%3D%20%5Cfrac%7B%7B%7Be%5E%7B%20-%20%5Clambda%20%7D%7D%7B%7B%5Cleft%28%20%7B10%7D%20%5Cright%29%7D%5Ex%7D%7D%7D%7B%7Bx%21%7D%7D)
Part a:
The probability that there are no arrivals in one minute is calculated by substituting x = 0 in the formula as,
![\begin{array}{c}\\P\left( {X = 0} \right) = \frac{{{e^{ - 10}}{{\left( {10} \right)}^0}}}{{0!}}\\\\ = {e^{ - 10}}\\\\ = 0.000045\\\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bc%7D%5C%5CP%5Cleft%28%20%7BX%20%3D%200%7D%20%5Cright%29%20%3D%20%5Cfrac%7B%7B%7Be%5E%7B%20-%2010%7D%7D%7B%7B%5Cleft%28%20%7B10%7D%20%5Cright%29%7D%5E0%7D%7D%7D%7B%7B0%21%7D%7D%5C%5C%5C%5C%20%3D%20%7Be%5E%7B%20-%2010%7D%7D%5C%5C%5C%5C%20%3D%200.000045%5C%5C%5Cend%7Barray%7D)
<em>The probability of no arrivals in a one-minute period is 0.000045.</em>
Part b:
The probability mass function of X can be written as,
![P\left( {X = x} \right) = \frac{{{e^{ - \lambda }}{\lambda ^x}}}{{x!}};x = 0,1,2, \ldots](https://tex.z-dn.net/?f=P%5Cleft%28%20%7BX%20%3D%20x%7D%20%5Cright%29%20%3D%20%5Cfrac%7B%7B%7Be%5E%7B%20-%20%5Clambda%20%7D%7D%7B%5Clambda%20%5Ex%7D%7D%7D%7B%7Bx%21%7D%7D%3Bx%20%3D%200%2C1%2C2%2C%20%5Cldots)
The probability of the arrival of three or fewer passengers in one minute is calculated by substituting \lambda = 10λ=10 and x = 0,1,2,3x=0,1,2,3 in the formula as,
![\begin{array}{c}\\P\left( {X \le 3} \right) = \sum\limits_{x = 0}^3 {\frac{{{e^{ - \lambda }}{\lambda ^x}}}{{x!}}} \\\\ = \frac{{{e^{ - 10}}{{\left( {10} \right)}^0}}}{{0!}} + \frac{{{e^{ - 10}}{{\left( {10} \right)}^1}}}{{1!}} + \frac{{{e^{ - 10}}{{\left( {10} \right)}^2}}}{{2!}} + \frac{{{e^{ - 10}}{{\left( {10} \right)}^3}}}{{3!}}\\\\ = 0.000045 + 0.00045 + 0.00227 + 0.00756\\\\ = 0.0103\\\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bc%7D%5C%5CP%5Cleft%28%20%7BX%20%5Cle%203%7D%20%5Cright%29%20%3D%20%5Csum%5Climits_%7Bx%20%3D%200%7D%5E3%20%7B%5Cfrac%7B%7B%7Be%5E%7B%20-%20%5Clambda%20%7D%7D%7B%5Clambda%20%5Ex%7D%7D%7D%7B%7Bx%21%7D%7D%7D%20%5C%5C%5C%5C%20%3D%20%5Cfrac%7B%7B%7Be%5E%7B%20-%2010%7D%7D%7B%7B%5Cleft%28%20%7B10%7D%20%5Cright%29%7D%5E0%7D%7D%7D%7B%7B0%21%7D%7D%20%2B%20%5Cfrac%7B%7B%7Be%5E%7B%20-%2010%7D%7D%7B%7B%5Cleft%28%20%7B10%7D%20%5Cright%29%7D%5E1%7D%7D%7D%7B%7B1%21%7D%7D%20%2B%20%5Cfrac%7B%7B%7Be%5E%7B%20-%2010%7D%7D%7B%7B%5Cleft%28%20%7B10%7D%20%5Cright%29%7D%5E2%7D%7D%7D%7B%7B2%21%7D%7D%20%2B%20%5Cfrac%7B%7B%7Be%5E%7B%20-%2010%7D%7D%7B%7B%5Cleft%28%20%7B10%7D%20%5Cright%29%7D%5E3%7D%7D%7D%7B%7B3%21%7D%7D%5C%5C%5C%5C%20%3D%200.000045%20%2B%200.00045%20%2B%200.00227%20%2B%200.00756%5C%5C%5C%5C%20%3D%200.0103%5C%5C%5Cend%7Barray%7D)
<em>The probability of three or fewer passengers arrive in a one-minute period is 0.0103.</em>
Part c:
Consider the random variable Y to denote the passengers arriving in 15 seconds. This means that the random variable Y can be defined as ![\frac{X}{4}](https://tex.z-dn.net/?f=%5Cfrac%7BX%7D%7B4%7D)
![\begin{array}{c}\\E\left( Y \right) = E\left( {\frac{X}{4}} \right)\\\\ = \frac{1}{4} \times 10\\\\ = 2.5\\\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bc%7D%5C%5CE%5Cleft%28%20Y%20%5Cright%29%20%3D%20E%5Cleft%28%20%7B%5Cfrac%7BX%7D%7B4%7D%7D%20%5Cright%29%5C%5C%5C%5C%20%3D%20%5Cfrac%7B1%7D%7B4%7D%20%5Ctimes%2010%5C%5C%5C%5C%20%3D%202.5%5C%5C%5Cend%7Barray%7D)
That is,
![Y\sim {\rm{Poisson}}\left( {\lambda = 2.5} \right)](https://tex.z-dn.net/?f=Y%5Csim%20%7B%5Crm%7BPoisson%7D%7D%5Cleft%28%20%7B%5Clambda%20%3D%202.5%7D%20%5Cright%29)
So, the probability mass function of Y is,
![P\left( {Y = y} \right) = \frac{{{e^{ - \lambda }}{\lambda ^y}}}{{y!}};x = 0,1,2, \ldots](https://tex.z-dn.net/?f=P%5Cleft%28%20%7BY%20%3D%20y%7D%20%5Cright%29%20%3D%20%5Cfrac%7B%7B%7Be%5E%7B%20-%20%5Clambda%20%7D%7D%7B%5Clambda%20%5Ey%7D%7D%7D%7B%7By%21%7D%7D%3Bx%20%3D%200%2C1%2C2%2C%20%5Cldots)
The probability that there are no arrivals in the 15-second period can be calculated by substituting the value of (λ=2.5) and y as 0 as:
![\begin{array}{c}\\P\left( {X = 0} \right) = \frac{{{e^{ - 2.5}} \times {{2.5}^0}}}{{0!}}\\\\ = {e^{ - 2.5}}\\\\ = 0.0821\\\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bc%7D%5C%5CP%5Cleft%28%20%7BX%20%3D%200%7D%20%5Cright%29%20%3D%20%5Cfrac%7B%7B%7Be%5E%7B%20-%202.5%7D%7D%20%5Ctimes%20%7B%7B2.5%7D%5E0%7D%7D%7D%7B%7B0%21%7D%7D%5C%5C%5C%5C%20%3D%20%7Be%5E%7B%20-%202.5%7D%7D%5C%5C%5C%5C%20%3D%200.0821%5C%5C%5Cend%7Barray%7D)
<em>The probability of no arrivals in a 15-second is 0.0821.</em>
Part d:
The probability that there is at least one arrival in a 15-second period is calculated as,
![\begin{array}{c}\\P\left( {X \ge 1} \right) = 1 - P\left( {X < 1} \right)\\\\ = 1 - P\left( {X = 0} \right)\\\\ = 1 - \frac{{{e^{ - 2.5}} \times {{2.5}^0}}}{{0!}}\\\\ = 1 - {e^{ - 2.5}}\\\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bc%7D%5C%5CP%5Cleft%28%20%7BX%20%5Cge%201%7D%20%5Cright%29%20%3D%201%20-%20P%5Cleft%28%20%7BX%20%3C%201%7D%20%5Cright%29%5C%5C%5C%5C%20%3D%201%20-%20P%5Cleft%28%20%7BX%20%3D%200%7D%20%5Cright%29%5C%5C%5C%5C%20%3D%201%20-%20%5Cfrac%7B%7B%7Be%5E%7B%20-%202.5%7D%7D%20%5Ctimes%20%7B%7B2.5%7D%5E0%7D%7D%7D%7B%7B0%21%7D%7D%5C%5C%5C%5C%20%3D%201%20-%20%7Be%5E%7B%20-%202.5%7D%7D%5C%5C%5Cend%7Barray%7D)
![\begin{array}{c}\\ = 1 - 0.082\\\\ = 0.9179\\\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bc%7D%5C%5C%20%3D%201%20-%200.082%5C%5C%5C%5C%20%3D%200.9179%5C%5C%5Cend%7Barray%7D)
<em>The probability of at least one arrival in a 15-second period is 0.9179.</em>