# Social Networks | NPTEL | Week 10 Assignment Solutions

This set of MCQ(multiple choice questions) focuses on the Social Networks NPTEL Week 10 Assignment Solutions.

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### Social Networks NPTEL 2022 Week 10 Assignment Solutions

Q1. Suppose that a person carrying a new disease enters a population, and transmits it to each person he meets independently with a probability of p. Further, suppose that he meets k people while he is contagious. What is the expected number of secondary infections produced?

a) p
b) k
c) p x k
d) pk

Q2. Consider the network as shown in Figure 1. Initially, the two nodes shown in red color are infected. Assume that the probability of infection across every edge, i.e. p is 2/3 and the infectious period TI is 1. What is the probability that the infection does not pass on from layer-1 to layer-2?

a) 2/3
b) 1/3
c) (2/3)4
d) (1/3)4

Q3. 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 pp, 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

a) iff there is a path consisting of blocked edges from any of the initially infected nodes to w
b) iff there is a path consisting of open edges from any of the initially infected nodes to w
c) iff there is a path from any of the initially infected nodes to w. The path may consist of any edgesopen/ blocked.
d) iff there does not exist any path from any of the initially infected nodes to w

Q4. In a tree network (shown in Figure 2), given that the probability of infection across every edge is p and every node has k children, the basic reproductive number R0 is denoted by the formula

a) R0 = p
b) R0 = k
c) R0 = p x k
d) R0 = pk

Q5. What is the full form of SIR epidemic model?

a) Susceptible-Influenced-Recovered
b) Susceptible-Infected-Recuperated
c) Susceptible-Infected-Recovered
d) Susceptible-Influenced-Recuperated

Social Networks NPTEL Week 10 Assignment Solutions

Q6. Consider the following two cases:
Case 1- Basic reproductive number is less than 1.
Case 2- Basic reproductive number is greater than 1.
Choose the correct statement from the following:

a) In case 1, the disease dies away with a probability 1; while in case 2, the disease persists in the population with a probability greater than 0.
b) In case 1, the disease dies away with a probability greater than 0; while in case 2, the disease persists in the population with a probability equal to 1.
c) In case 1, the disease persists in the population with a probability greater than 0; while in case 2, the disease dies away with a probability 1.
d) In case 1, the disease persists in the population with a probability 1; while in case 2, the disease dies away with a probability greater than 0.

Q7. Choose the correct statement from the following.

a) Both SIR and SIS model can run for an infinite number of steps on a network.
b) Both SIR and SIS model should come to an end after running for a finite number of steps on a network.
c) SIS model should come to an end after running for a finite number of steps on a network, while SIR model can keep running indefinitely on a network.
d) SIR model should come to an end after running for a finite number of steps on a network, while SIS model can keep running indefinitely on a network.

Social Networks NPTEL Week 10 Assignment Solutions

Q8. Consider a disease â€™Xâ€™. People who are diagnosed in the earlier stage have high chance of recovery. But the intense infection of â€™Xâ€™ will lead to death. The recovered people also stand a chance to get infected again. What kind of model does this disease â€™Xâ€™ exhibit?

a) SIS
b) SIR
c) Both SIS and SIR
d) Neither SIS nor SIR

Social Networks NPTEL week 10 Assignment Solutions

Q9. In the modelling of mitochondrial eve using Wright-Fischer number

a) Population size can be anything in any generation.
b) Population size doubles every generation.
c) Population size remains the same in every generation.
d) Population size halves every generation.

Q10. Suppose that a person carrying a new disease enters a population, and transmits it to each person he meets independently with a probability of 9/20. Further, suppose that he meets 1000 people from the population while he is contagious. What is the expected number of secondary infections produced?

a) 1000^0.45
b) 450
c) 1000
d) 45

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