Question

The empirical rule states if an distribution is symmetrical and bell-shaped, approximately _______, 95%, and 99.7% of its data values will fall within one, two, and three standard deviations above and below the mean, respectively.

Answer 1

In Statistics, application of the empirical rule can be applied to the empirical formula for calculating the mean and standard deviation of values given.
In normal "symmetrical" and bell-shaped distribution, approximately 68% of values fall within one standard deviation above and below the mean.
68% of values fall => m ± 1 sd
95% of values fall => m ± 2sd
99.7% values fall => m ± 3sd