Social Networks | Week 10

Session: JULY-DEC 2023

Course Name: Social Networks

Course Link: Click Here

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q1. Consider the example of Book sales for the power law distribution where we plot a graph between the popularity of the book and sales. We observe the top ranked books have high sales and the low ranked books have very low sales. Assuming that Best seller books constitute 20 percent of sales, which of the following is true?
Selling only Best seller books is profitable
Selling niche books is will be a loss
Selling both Best sellers and Niche books is profitable
all of the above

Answer: Selling both Best sellers and Niche books is profitable

Q2. Consider a tree structures network where every node has 5 children and the probability of a node infecting the other is 0.8. Calculate the number of child nodes infected by a single node at level 1.
5
4
3
2

Answer: 4

Q3. Consider a branching model of network where every node has 5 children and the probability of transmission of an infection is 0.4, what is the probable number of people infected at level 4?
24
16
20
5

Answer: 16

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q4. Which of the following is true for Basic reproductive number?
It is the number of people infected by a single infected person
It is the number of people with ample immunity to an infection
It is the number of people who can recover from an infection
It is the probability of disease transmission

Answer: It is the number of people infected by a single infected person

Q5. In a SIS model, if probability of spreading disease is 1/3, what will be the probability that a person who recovered from the disease is likely to get infected again?
0
1
1/3
2/3

Answer: 1/3

Q6. Consider a disease ‘A’. People who are diagnosed in the earlier stage have high chance of recovery. But the intense infection of ‘X’ will lead to death. The recovered people also do not stand a chance to get infected again. What kind of model does this disease ‘X’ exhibit?
SIR
SIS
Both SIR and SIS
Neither SIR nor SIS

Answer: SIR

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q7. In the percolation model (static view of the SIR model), assume that TI=1. For every edge Eu,v
in the network, we toss a biased coin which shows head with a probability of p, which is the infection rate of the disease, i.e., the probability that v will become infected in the next iteration, given that u is infected. If head turns up, we assume an edge to be open, else blocked. According to this percolation model, a node w in the network will become infected
iff there is a path consisting of blocked edges from any of the initially infected nodes to w.
iff there is a path consisting of open edges from any of the initially infected nodes to w.
iff there is a path from any of the initially infected nodes to w. The path may consist of any edgesopen/ blocked.
iff there does not exist any path from any of the initially infected nodes to w.

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q1. Choose the correct option based on the given statements. Statement I – A disease’s spread depends on whether the network is sparsely connected or densely. Statement II – A disease’s spread depends on its degree of contagiousness.
a. I only is True
b. II only is True
c. Both are True
d. None is True

Answer: c. Both are True

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q2. Consider the following network D where node A if infected with a disease and the probability of spreading a disease from node A to its connected nodes is 0.6. If the disease starts spreading from node A, then the expected number of nodes with the disease is

a. 2
b. 3
c. 4
d. 5

Answer: b. 3

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q3. Given the reproductive number of an epidemic is R0< 1, Comment about the disease spread in the network.
a. The disease dies out with a positive probability
b. The disease persists with a positive probability
c. The disease persists forever in the network
d. The disease dies out with probability 1

Answer: d. The disease dies out with probability 1

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q4. Consider a disease ‘X’. People who are diagnosed in the earlier stage have high chance of recovery. But the intense infection of ‘X’ will lead to death. The recovered people do not have a chance to get infected again. What kind of model does this disease ‘X’ exhibit?
a. SIS
b. SIR
c. Both
d. None

Answer: b. SIR

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q5. Suppose the basic reproductive number is estimated to be R0 = 1.5. If a vaccine giving 100% immunity is available next time and a fraction v = 0.3 of randomly selected individuals were vaccinated, an estimate of the new reproductive number would be
a. 1.05
b. 1.1
c. 1.2
d. 1.3

Answer: a. 1.05

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q6. Given that the Reproductive number of an epidemic in action is 1.1. What are valid attempts to curb the disease or reduce the reproductive number?
a. Isolate the infected person so that we reduce the number of people getting infected.
b. Create awareness among the population to follow proper hygiene thereby reducing the probability of the disease spread
c. Avoid visiting public gatherings to reduce contact probability with infected persons
d. All the above

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Answer: d. All the above

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q7. In the percolation model, it is possible to find if a node will be infected or not without any notion of time. When can you say that a node ‘A’ is susceptible for infection in a percolation model?
a. If there exists at least one path with all open edges from the infected node to the node ‘A’
b. If there exists at least one path with one open edge from the infected node to the node ‘A’
c. If there exists more than one path with one open edge from the infected node to the node ‘A’
d. If there exists at least one path with all closed edges from the infected node to the node ‘A’

Answer: a. If there exists at least one path with all open edges from the infected node to the node ‘A’

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q8. Which of the following model can run for infinite number of steps in a network?
a. SIR
b. SIS
c. Both
d. None

Answer: b. SIS

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q9. Given the probability of spreading disease is 0.4, what is the probability that the same person does not get infected for the second time?
a. 0.4
b. 0.6
c. 0.8
d. 1

Answer: b. 0.6

These are Nptel Social Networks Week 10 Assignment 10 Answers

Q10. Suppose that a person ‘P1’ gets infected with a contagious disease and transmits it to each person he meets independently with a probability of 0.64. Further, suppose that he comes in contact with 450 people from the population while he is contagious. What is the expected number of secondary infections produced?
a. 450
b. 288
c. 29
d. 64

Answer: b. 288

These are Nptel Social Networks Week 10 Assignment 10 Answers

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