Home > Statistics Every Writer Should Know > The Stats Board > Discusssion
Is it a normal distribution???
Message posted by Faraaz Mir on April 6, 2000 at 12:00 AM (ET)
How do you know if your data
represents normal distribution?
I have heard the words Skew and
Kurtosis mentioned but am unware
of what there results represent.
Any help will be appreciated.
READERS RESPOND:
(In chronological order. Most recent at the bottom.)
Re: Is it a normal distribution???
Message posted by nancy diehl on April 7, 2000 at 12:00 AM (ET)
First of all, the best way to determine if the data is normal is by looking
at it visually, either with a normal probability plot, stem & leaf diagram
or a histogram. The distribution should resemble what is referred to as
a "bell shape."Tests for normality can be performed to determine the probability the sample
came from a normally distributed population by using the Kolmogorov-Smirnov
test, or the Shapiro-Wilks' W test. However, a visual examination of the data
is generally most useful.
Measures of Kurtosis and Skewness:
Kurtosis measures the "peakedness" of a distribution. If the kurtosis is
different from 0, then the distribution is either flatter or more peaked
than a normal. The kurtosis of a normal distribution is 0.
Skewness measures the deviation of the distribution from symmetry.
If the skewness is different from 0, then that distribution is asymmetrical.
Normal distributions are perfectly symmetrical. The mean=the median=the mode
for a normal distribution; which is not the case if the distribution is
skewed.
Re: Is it a normal distribution???
Message posted by Tony Gebhardt on April 12, 2000 at 12:00 AM (ET)
If you want to give us an example of the problem you are working on we can try to answer your query. It is relatively easy to do the calcs, but if you got the accurate info, we can do a bell diagram and by example show you how to arrive at the answer.
Re: Is it a normal distribution???
Message posted by J. Borden on April 13, 2000 at 12:00 AM (ET)
IF YOU CAN FIND A STATISICS TEXT BOOK, (ONE YOU WOULD USE IN COLLEGE) YOU SHOULD BE ABLE TO FIND SOMETHING IN RELATION TO "USING THE GOODNESS OF FIT TEST TO TEST NORMALITY. IT KINDA GOES ALONG USING CHI-SQUARE CALCULATIONS...HOPE THIS HELPS..
Your $5 contribution helps cover part the $500 annual cost of keeping this site online.
