According to the empirical rule, in a normal distribution, approximately % of the data lie within plus or minus 1 standard deviation of the mean, approximately % of the data lie within plus or minus 2 standard deviations of the mean, and approximately % of the data lie within plus or minus 3 standard deviations of the mean.

According to the empirical​ rule, in a normal​ distribution, approximately​ 68 % of the data lie within plus or minus 1 standard deviation of the​ mean, approximately​ 95 % of the data lie within plus or minus 2 standard deviations of the​ mean, and approximately​ 99.7 % of the data lie within plus or minus 3 standard deviations of the mean.