Probability Simulator

About the Probability Simulator

Flip a coin ten times and you might get seven heads. Flip it a thousand times and you'll land much closer to half. This simulator lets students actually generate that data — for a coin, a single die, or the sum of two dice — and watch the experimental results converge toward the theoretical probability as the trial count grows.

Each outcome gets its own bar showing the experimental percentage next to the theoretical one, so the gap between what happened and what should happen is visible rather than just stated.

How to use it in your classroom

1. Choose an experiment: a coin flip, a single die, or the sum of two dice.
2. Click Roll Once for a single trial, or Roll 10 / Roll 100 to generate data faster.
3. Compare the experimental percentage to the theoretical percentage for each outcome.
4. Hit reset to clear the data and start a new run.

Tips from the classroom

• Have students predict the theoretical percentages before rolling, especially for the two-dice sum, where 7 is far more likely than 2 or 12.
• Run only 10 rolls first and let students see how far the experimental bars can swing from theoretical, then run 100 more and watch them settle down.
• The two-dice sum experiment is the one that best shows unequal probabilities, since there's only one way to roll a 2 but six ways to roll a 7.
• Reset between groups or class periods so each run starts from zero rather than inheriting the previous class's data.

Frequently asked questions