68-95-99-7-rule Definition
noun
(singular only, statistics) The rule that a normal distribution will have 68% of its observations within one standard deviation of the mean, 95% within two, and 99.7% within three.
Wiktionary
(singular only, statistics) The rule that a normal distribution will have 68% of its observations within one standard deviation of the mean, 95% within two, and 99.7% within three.
