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variables that follow the normal distribution form a bell-shape curve called the Gaussian. Variables that do not follow the normal distribution tend to form a more different curve that varies significantly from the Gaussian, the curves of non-normal distributions include skew, kurtosis, etc.
examples of variables that do not form a normal distribution include the vertical height of male and female. When combined together, the distribution is binomial but turns to be normal distribution if heights are done in separate tests
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