In this assignment you will experience the system dynamics modeling process by exploring the propagation of an infectious disease through a population of susceptible individuals. Infectious diseases present critical management and public policy challenges (consider SARS, MERS, Avian influenza, HIV, or the threat of bioterror attack). They also provide a useful setting to explore feedbackhow the states of a system (the levels or stocks) influence (or feed back to) the flows that alter those states. The assignment also introduces you to the structure and behavior of fundamental feedback systems. These systems are the building blocks from which more complex systems are composed. In particular, the feedback structure governing the spread of contagious disease can also help to explain the growth of new products, the diffusion of innovations, the spread of financial panics, and other forms of social contagion important in business settings. The assignment gives you practice with the concepts of dynamic modeling and the modeling process while enabling familiarity with the modeling software we will use. You are to work on this assignment individually, and submit your individual work and writeup via the course website.

A. Get the Software

Weve mentioned that there are several excellent software packages available for dynamic modeling. For our work this semester we will use the VensimPLE software. Your syllabus and Assignment 0 explained how to download and install the program.

B. Become Familiar with the Software and Build and Explore the Base Model

Download both and the datafile , which contains data for the Taiwanese SARS epidemic as a Vensim Data File (.vdf). Put the SARSDATA file in your Vensim directory. The tutorial walks you though the development of the epidemic model step by step and shows you how to use the data.

Answer the following three questions.

A ) What happens when you initialize the stock of infected people at zero? Briefly explain how you account for the behavior you observed with reference to the models structure (remember, structure drives behavior). How do the dynamics change if you assume that one or more members of the population in question are already infected?

B) How do the dynamics change as the contact frequency increases? Does changing the contact frequency influence the total number of people who get SARS? Explain why or why not with reference to the structure of the model.

c)How do the dynamics change as infectivity varies? Explain

Submit your answers to the above questions in a brief writeup: each answer may be a few sentences and involve a handful of model runs. To back up your points, show only a few graphs, tables, or any form of result summary based on model output. You need not show all model runs you have donejust select the minimum you need to answer the questions concisely.

Note: Place relevant selections of models and graphs next to your answers to a given question. Placing graphs in an appendix makes it harder to follow your logic (and to grade your work appropriately)