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What is a Fair Coin?
A fair coin has exactly 50% probability of landing on Heads and 50% on Tails. Each flip is independent - previous results don't affect future flips.
Key principle: The coin has no memory. Past flips don't influence future outcomes.
The Gambler's Fallacy
The gambler's fallacy is the mistaken belief that past random events affect future probabilities.
Example: After 5 heads in a row, many people think tails is "due" - but the next flip still has exactly 50% chance of heads!
This simulator helps visualize this concept by tracking streaks and showing that unlikely runs happen naturally in random sequences.
Streaks and Runs
- Streak: Consecutive identical outcomes (e.g., HHHH is a 4-heads streak)
- Run: Any sequence of consecutive identical outcomes
- Expected behavior: In 100 flips, expect to see runs of 5-7 in a row
- Surprising fact: Long streaks are more common than intuition suggests
Biased Coins
A biased coin has unequal probabilities for heads and tails. Real coins can be slightly biased due to:
- Weight distribution (design asymmetry)
- Wear and damage
- Flipping technique
Use the bias slider to simulate unfair coins and see how bias affects long-term proportions.
Law of Large Numbers
As the number of flips increases, the proportion of heads approaches the true probability (0.5 for fair coin).
Important: This doesn't mean short-term runs "balance out" - it means the percentage gets closer to 50%, not that the count difference gets smaller.
Example:
- 10 flips: 7H, 3T (70% heads) - not unusual
- 1000 flips: 520H, 480T (52% heads) - closer to 50%
- 10000 flips: 5020H, 4980T (50.2% heads) - very close to 50%
Applications
- Decision Making: Fair, random choices between two options
- Sports: Determining possession, serve, etc.
- Education: Teaching probability and statistics
- Gaming: 50/50 chance mechanics
- Cryptography: Generating random bits
- Simulation: Binary random processes
Statistics Explained
- Heads/Tails Count: Total number of each outcome
- Proportion: Percentage of each outcome (should approach 50% for fair coin)
- Longest Streak: Maximum consecutive identical flips
- Number of Runs: How many streaks occurred
- Average Run Length: Mean streak length
- Alternations: How often the result switched (H→T or T→H)