Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

SIS Epidemic Modelling

  1. May 9, 2013 #1
    For the probability of the number of infective's increasing in one time step, I found the answer is:
    ∆tβi(N-i)/N
    where β is the contact rate, ∆t is the time step, i is number of infectives,N is total number of susceptible's and infective's

    I can't quite see where this is coming from. β is the contact rate, so it makes sense to multiply by i since for more i, more chances of encounters. Then multiplying by N-i makes sense since more susceptible also means more chance of encounters.

    But then why the division by N? I think my problem may be in understanding what the "contact rate" actually means
     
  2. jcsd
  3. May 10, 2013 #2
    I think it actually has to do with understanding what a probability is. :tongue:

    What is a probability? What does it tell you?

    Answering those questions should tell you the answer to your question.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: SIS Epidemic Modelling
  1. ARMA model (Replies: 3)

  2. Aggregate model (Replies: 1)

  3. Empirical models (Replies: 5)

Loading...