What is the "Three-Standard-Deviations Rule"

Question

This rule is also known as the "68–95–99.7 rule".  What does this rule stand for and how does it help me?

Answer 1

This rule is used to remember the percentage of values that lie around the mean in a normal distribution. 

It is a helpful rule to quickly analyze a normal distribution. 

To reiterate, 68% of the data is within 1 standard deviation, 95% is within 2 standard deviations, 99.7% is within 3 standard deviations