Math
Normal distribution.
Definition
A symmetric, bell-shaped probability distribution where data clusters around the mean. About 68% of data falls within 1 standard deviation of the mean, 95% within 2, and 99.7% within 3.
Examples
Real-world.
- 1 Heights of adult males in a population
- 2 Scores on a standardized test like the SAT
- 3 Measurement errors in scientific experiments
Key Fact
68-95-99.7 rule (Empirical Rule): 68% within ±1σ, 95% within ±2σ, 99.7% within ±3σ