distribution anatomy

empirical rule

applies to any set of data that follows a normal distribution.

• About 68% of your values lie within 1 standard deviation of the mean.
• About 95% of your values lie within 2 standard deviations of the mean.
• About 99.7% of your values lie within 3 standard deviations of the mean.
  

chebyshev's rule

for any distribution

• At least 75% of your values lie within 2 standard deviations of the mean.
• At least 89% of your values lie within 3 standard deviations of the mean.
• At least 94% of your values lie within 4 standard deviations of the mean.

Sources: 1