Epidemic Simulator

An experimental probability exercise.


Be a Researcher

This simulator allows you to model a simplified epidemic. When you click Run, the simulation will advance day-by-day. Each day, a villager has a chance of moving into an empty adjacent space on the grid. If healthy, non-immune villagers come into contact with an infected person, they have a chance of catching the disease, unless that person is quarantined. Once the disease has run its course in a villager, they have a chance of recovering or dying. You can tweak all of these variables, and more, and observe how the epidemic changes.

Each time you conduct a trial the results will appear in the table, and the mean and standard deviation will update. You can clear these results at any time. Note that if you pause a trial and adjust the variables, the simulation will regenerate the grid and reset to Day 0.

Make a Hypothesis

Rigorous research means trying to isolate the effect a single variable has on a situation by “controlling” for the other variables. To begin to understand how any of these variables affect the epidemic, try the following:

  1. Conduct a number of trials, and record the results.
  2. Change one variable (e.g., grid dimensions).
  3. Make a hypothesis about how your change will affect the outcome of the experiment. Here are some examples, each of different complexity:
    • If I increase the size of the village, fewer people will die.
    • If I increase the size of the village, the disease will take longer to spread, so fewer people will catch it before the infected die or recover.
    • If I decrease the size of the village, the epidemic will not last as long, because the disease will spread and then die out more quickly.
  4. Conduct the same number of trials as you did in the first experiment and record the results.
  5. Compare the mean and standard deviations between the two experiments. Do the data support your hypothesis?
  6. Decide on another variable to change, and repeat!

Simulation Output



Day 0


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Duration (days) Death count Number who never got ill Number who got ill and recovered
Default variables. View all variables for this round.
Standard Deviation

Variables changed since the last round of trials are in bold.