# Question #ab446

##### 1 Answer

Dec 17, 2017

A non normal distribution is a distribution that is not normal.

Normal distribution has following basic properties: it is symmetric, unimodal (only one peak) and bell shaped. When we use the term "non normal", we mean that either the distribution is skewed (not symmetric) or is has two means, or the shape is not similar to bell shape. But what we really mean from "non normal" term is that normality assumption does not hold, and we cannot use z-table without normality.

Note that even if population is non normal, sample mean could be normally distributed if sample size is large enough because of Central Limit Theorem.