Probability
Probability is a way to measure how likely something is to happen.
Rolling a single die: six faces, one shows a 3. The chance of rolling a 3 is 1 out of 6 — about 0.17. Higher numbers mean more likely; zero means impossible; one means certain.
Explaining probability by grade level
Roll one die and guess which number comes up. Sometimes you guess right, sometimes you do not. Each number has the same chance. That means no single number shows up more than the rest over many rolls.
Projects that explore probability
Each face of a fair die has exactly a one-in-six chance of landing face up — yet when you roll only a few times, the results often look uneven. Small samples allow wide variation, so the numbers can seem off. Roll one die 100 times, though, and the actual frequencies pull closer to that predicted one-in-six split.
In a two-player Monopoly game, dice rolls dominate the outcome so completely that a Type A aggressive player and a Type B cautious player win nearly the same number of games. Strategy differences barely matter when chance controls so much. Add a third player and the balance shifts — with more agents in the game, personality differences produce unequal win rates, showing that strategy can override pure probability under the right conditions.
If each baseball game were an independent coin flip, how often should winning streaks occur? A Monte Carlo simulation generates thousands of random seasons to set that baseline. When you compare real streak counts against those predictions at the 95% confidence level, real streaks exceed the random model — revealing that non-random factors, not just chance, are shaping outcomes.
At each peg inside a Galton board, a marble has a roughly equal chance of bouncing left or right. After many such bounces, those tiny random deflections add up. Drop 200 marbles and something predictable emerges: about 50% land in the two center slots, and the overall spread forms a bell curve — a pattern you can predict before a single marble falls.
