The Idea of Probability

When you flip a coin, there are only two possible outcomes, heads or tails. On any one flip, you will observe one outcome or another—heads or tails. Over a large number of flips, though, the proportion of heads and tails will come to approximate the probability of each outcome.

In this applet, you can set the probability of heads for your virtual coin, then flip it any number of times. Notice how the proportion of flips that produce heads can be quite variable at first, but will eventually settle down to the probability.