Normal Distribution
Message posted by mitch on September 30, 1999 at 12:00 AM (ET)

my questions for a survey are usually categorical or nominal data.question: for variables like age, sex, educ attainment...do i need to know if they are distributed normally? what's the diff. bet norma l and uniform distribution?how can i apply normality in purely categorical data?in a sample of 400, do i have to know if it is normaly distributed? cant i make any statistical comp. if the data is not distributed normally?

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Re: Normal Distribution
Message posted by Bill on October 1, 1999 at 12:00 AM (ET)

I assume you know the characteristics of a normal distribution. Now, suppose that we take an infinitely large population of random numbers that are EVENLY distributed between zero and 100. The population will have a uniform distribution, that is, every number between zero and 100 will be equally likely. I think that this is also called a rectangular distribution.

In any sample, regardless of size, you need to know if a variable is normally distributed if you plan to apply a statistical test that is based on the normal distribution. The concept of normality applies to variables, not the sample. Yes, you can make statistical comparisons if the data is not normally distributed if you use statistical tests which do not make assumptions about the distribution of the data, i.e., nonparametric or distribution-free tests.