Empirical Rule

Empirical Rule (also known as the 68-95-99.7 Rule)

In a Normal Distribution with mean μ and standard deviation σ:

• Approximately 68% of the observations fall within σ of the mean μ.
• Approximately 95% of the observations fall within 2σ of the mean μ.
• Approximately 99.7% of the observations fall within 3σ of the mean μ.

This result is known as the empirical rule.

contributed by Katie Ciskowski

Reference:

Daren, S. S., & Tabor, J. (2020). Updated version of the practice of Statistics (Teachers Edition) (Sixth Edition). W H Freeman & CO LTD.