Data from 14 cities were combined for a 20-year period, and the total 280 city-years included a total of 107 homicides. After finding the mean number of homicides per city-year, find the probability that a randomly selected city year has the following numbers of homicides, then compare the actual results to those expected by using the Poisson probabilities a. P(0) = (Round to four decimal places as needed.) b. P(1) = (Round to four decimal places as needed.) c, P(2) = (Round to four decimal places as needed.)d. P(3) = (Round to four decimal places as needed.)

Respuesta :

Answer:

a) P(0) = 0.6824

b) P(1) = 0.2608

c) P(2) = 0.0498

d) P(3) = 0.00635

Step-by-step explanation:

Number of units (n) in the data, n = 280

Total number of events, k = 107

The probability using Poisson probabilities is calculated using the formula;

P(x) = [tex]\frac{e^{-\lambda}\lambda^x}{x!}[/tex]

here,

Poisson parameter, λ = [tex]\frac{107}{280}[/tex]

Thus,

a) P(0) = [tex]\frac{e^{-\frac{107}{280}}(\frac{107}{208})^0}{0!}[/tex]

or

P(0) = 0.6824

b) P(1) = [tex]\frac{e^{-\frac{107}{280}}(\frac{107}{280})^1}{1!}[/tex]

or

P(1) = 0.2608

c) P(2) = [tex]\frac{e^{-\frac{107}{280}}(\frac{107}{280})^2}{2!}[/tex]

or

P(2) = 0.0498

d) P(3) = [tex]\frac{e^{-\frac{107}{280}}(\frac{107}{280})^3}{3!}[/tex]

or

P(3) = 0.00635

Using the Poisson distribution, we find that:

a) P(0) = 0.6824.

b) P(1) = 0.2608.

c) P(2) = 0.0498.

d) P(3) = 0.0064.

Poisson distribution:

[tex]P(X = x) = \frac{e^{-\mu}\mu^{x}}{(x)!}[/tex]

The parameters are:

  • x is the number of successes.  
  • [tex]\mu[/tex] is the mean in the given interval.

In this problem, there are 107 homicides in 280 city-periods, thus:

[tex]\mu = \frac{107}{280} = 0.3821[/tex]

Item a:

[tex]P(0) = P(X = 0) = \frac{e^{-0.3821}(0.3821)^{0}}{(0)!} = 0.6824[/tex]

Item b:

[tex]P(1) = P(X = 1) = \frac{e^{-0.3821}(0.3821)^{1}}{(1)!} = 0.2608[/tex]

Item c:

[tex]P(2) = P(X = 2) = \frac{e^{-0.3821}(0.3821)^{2}}{(2)!} = 0.0498[/tex]

Item d:

[tex]P(3) = P(X = 3) = \frac{e^{-0.3821}(0.3821)^{3}}{(3)!} = 0.0064[/tex]

A similar problem is given at https://brainly.com/question/13971530