Normal Distributions

A statistical distribution that reflects a normal or typical randomness in the spread of data points around the central tendency. This distribution is often referred to as a "bell curve" because the shape looks like a bell due to the symmetrical spread of 50% of the data points on either side of the mean (i.e., the average or center of the distribution). The normality implies there is little or no bias nor skewness (i.e., non-normality) in the data. The normality of a distribution should be statistically validated such as in using an Anderson-Darling (AD) test of a Normality Test or Probability Plot.
Related StatStuff Videos: 
   -Section 5-Measure Phase, Lesson #8 - Distributions: Overview
   -Section 5-Measure Phase, Lesson #9 - Distributions: Normal