The empirical rule shows that 68% of the distribution lies within one standard deviation, in this case, from 11.6 to 14.6 years. Thus, the remaining 32% of the distribution lies outside this range.

Using the empirical rule, for example, if 100 test scores are collected and used in a normal probability distribution, 68% of those test scores should fall within one standard deviation above or ...

The bell curve, or normal distribution, ... This relationship is known as the 68-95-99.7 rule (or the empirical rule). ... Why is the curve shaped like a bell?

A lognormal distribution is a statistical distribution characterised by a skewed bell-shaped curve. It arises, for instance, when taking the exponential of a normally distributed variable.