Barabási: Ch. 10 — Spreading Phenomena

In the homogeneous-mixing SI model, which statement correctly describes the analytical solution for the time required to reach a fraction $i(t) = 0.5$?

a) It depends only on the total population size and not on the infection rate $𝛽$

b) It always occurs at the same time, regardless of the initial condition

c) It is inversely proportional to the contact density but not to $𝛽$

d) It increases linearly with the initial number of infected individuals

e) None of the above. 

Original idea by: Gabriel Sato