Question

In: Statistics and Probability

Currently, among the 20 individuals of a population, 2 have a certain infection that spreads as...

Currently, among the 20 individuals of a population, 2 have a certain infection that spreads as follows: Contacts between two members of the population occur in accordance with a Poisson process having rate ?. When a contact occurs, it is equally likely to involve any of the possible pairs of individuals in the population. If a contact involves an infected and a non-infected individual, then, with probability p the non-infected individual becomes infected. Once infected, an individual remains infected throughout. Let ?(?) denote the number of infected members of the population at time t. Considering the current time as t = 0, we want to model this process as a continuous-time Markov chain.

(a) What is the state space of this process?

(b) What is the probability that an infected person contacts a non-infected person?

(c) What is the rate at which an infected person contacts a non-infected person (we denoted this type of contact by I-N contact) when there are X infected people in the population?

(d) Is the inter-contact time between two I-N contacts exponentially distributed? Why?

(e) Compute the expected time until all members of the considered population are infected.

Solutions

Expert Solution

I have posted the handwritten solutions below along with brief typed explanations.
Please upvote and provide feedback if this answer helped you. This would help me improve and better my solutions.
I will be happy to answer your doubts, if any in the comment section below. Thanks! :)

(a) The state space X was derived as the number of infected persons in the population

The state space diagram and the explanation is provided below

(b) The probability that an infected person "contacts" a non-infected person was calculated as:

(c) The rate at which an infected person contacts a non-infected person was calculated as:

The derivation is given below in Page 2 and Page 3:

(d) The inter-contact time between two I-N contacts was derived to be exponentially distributed
with

  ,
  

(e) The Expected time untill all members of the considered population are infected was derived as:

The explanation is given below:


Related Solutions

With a town of 20 people, 2 have a certain disease that spreads as follows: Contacts...
With a town of 20 people, 2 have a certain disease that spreads as follows: Contacts between two members of the town occurred in accordance with a Poisson process having rate ?. When contact occurs, it is equally likely to involve any of the possible pairs of people in the town. If a diseased and non-diseased person interect, then, with probability p the non-diseased person becomes diseased. Once infected, a person remains infected throughout. Let ?(?) denote the number of...
The incidence of a deadly disease, among a certain population, is 0.01%. Individuals, randomly selected from...
The incidence of a deadly disease, among a certain population, is 0.01%. Individuals, randomly selected from this population are submitted to a test whose accuracy is 99% both ways. That is to say, the proportion of positive results among people known to be affected by the disease is 99%. Likewise, testing people that are not suffering from the disease yields 99% negative results. The test gives independent results when repeated. An individual test positive. a) What is the probability that...
2. [20] A population of Ladon dragons has a birth rate of 3.3 individuals / (individuals...
2. [20] A population of Ladon dragons has a birth rate of 3.3 individuals / (individuals x year) and a death rate of 3.2 individuals / (individuals x year). (a) What is r? (b) Based on your answer from part a, is the population growing, declining, or remaining constant? (c) Assuming exponential growth, how many years are necessary for the population to double? (d) On the Wondering Rock Mountain, the population is presently 49. What will the population be in...
A SIS disease spreads through a population of size K = 30, 000 individuals. The average...
A SIS disease spreads through a population of size K = 30, 000 individuals. The average time of recovery is 10 days and the infectious contact rate is 0.2 × 10^(−4) individuals^(−1) day^(−1) . (a) The disease has reached steady-state. How many individuals are infected with the disease? (b) What is the minimum percentage reduction in the infectious contact rate that is required to eliminate the disease? (c) By implementing a raft of measures it is proposed to reduce the...
A SIS disease spreads through a population of size K = 30, 000 individuals. The average...
A SIS disease spreads through a population of size K = 30, 000 individuals. The average time of recovery is 10 days and the infectious contact rate is 0.2 × 10^(−4) individuals^(−1) day^(−1) . (a) The disease has reached steady-state. How many individuals are infected with the disease? (b) What is the minimum percentage reduction in the infectious contact rate that is required to eliminate the disease? (c) By implementing a raft of measures it is proposed to reduce the...
The population of deer is currently 2,000 individuals. The population can be described by a logistic...
The population of deer is currently 2,000 individuals. The population can be described by a logistic model with K = 5,000 and r = ½. If 600 deer are hunted this season, will the population of deer go up, or down, or stay at 2,000? Is this harvest rate sustainable? What is the maximum sustainable yield? Explain.
In a certain population of mussels (Mytilus edulis), 80% of the individuals are infected with an...
In a certain population of mussels (Mytilus edulis), 80% of the individuals are infected with an intestinal parasite. A marine biologist plans to examine 100 randomly chosen mussels from the population. Find the probability that 85% or more of the sampled mussels will be infected using normal approximation to binomial distribution. What is the expected number of infected mussels in 50 randomly chosen mussels?
In a certain population of mussels (mytilus edulis) 80% of the individuals are infected with an...
In a certain population of mussels (mytilus edulis) 80% of the individuals are infected with an intestinal parasite. A marine biologist plans to examine 100 randomly chosen mussels from the population. Let ? represent the number of mussels in this sample with the intestinal parasite. 9) Clearly state the distribution that ? follows, Explain why you picked this distribution? State the distribution we may use to approximate it. 10) Approximate the probability that between 75% and 90% (inclusive) of the...
In a certain population of mussels (mytilus edulis) 80% of the individuals are infected with an...
In a certain population of mussels (mytilus edulis) 80% of the individuals are infected with an intestinal parasite. A marine biologist plans to examine 100 randomly chosen mussels from the population. Let ? represent the number of mussels in this sample with the intestinal parasite. 9) Clearly state the distribution that ? follows, Explain why you picked this distribution? State the distribution we may use to approximate it. 10) Approximate the probability that between 75% and 90% (inclusive) of the...
Allele frequency is the relative frequency of a certain allele type among a certain population. Suppose...
Allele frequency is the relative frequency of a certain allele type among a certain population. Suppose that within a certain area, the allele frequency of A, B and O are 0.2, 0.1, and 0.7, respectively. Suppose that when randomly picking up a person, the first allele type is independent of the second allele type regardless of the type. Calculate the following probabilities: • The probability for this person to have type O blood. • The probability for this person to...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT