If the population distribution of a variable is approximately normal, then according to the empirical rule, which of the following statements are correct?

A. Roughly 68% of the values are within one standard deviation of the mean.

B. Roughly 95% of the values are within two standard deviations of the mean.

C. Roughly 99.7% of the values are within three standard deviations of the mean.

D. All of the above statements are correct.