If about 68 percent of values lie within one standard deviation, the share lying outside three deviations is roughly:

1. The empirical rule states how much lies inside each band. 2. About 99.7 percent of the x values lie within three standard deviations of the mean. 3. Everything else lies outside, which is 100 minus 99.7. 4. That leaves roughly 0.3 percent, or about three values in a thousand. 5. 5 percent is the share outside two deviations, and 32 percent the share outside one. _Source: OpenStax Introductory Statistics 2e (CC BY 4.0), Ch 6 'The Normal Distribution', sections 6.1-6.3_