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#1 Re: Help Me ! » Non-normal distribution.....calculating CI » 2014-04-07 21:02:02

Thanks guys.

Actually, the short article is the one that got me thinking and asking the professor that very question.
In his class, he shows a theoretical distribution of income that looks exactly like the one in the short article, a positively skewed distribution (mean is towards the lower income). There was no real data behind it and we were just debating on the estimating CI.  I said that since the data is skewed, we cannot use the Excel STDEV's value to mark the CI range.  He agrees.  But when I ask him how to define the CI for skewed distribution data.  He couldn't answer my question. 

As for the long article, I read it but didn't find the answer I was looking for, i.e., what is the income range that 95% of the population belongs to?

If I were to have the real data, I CAN calculate from the accumulative numbers of people at each income intervals and find out the answer to my question.

However, what I really want to know was how to use Excel to work on a set the sample non-normal distributed data to answer this question.

#2 Re: Help Me ! » Non-normal distribution.....calculating CI » 2014-04-07 13:55:56

sorry bobbym, I don't have the data.
This is just a theoretical question as I my professor couldn't answer my question regarding the use of CI from the normal distribution on a non-normal distribution data, i.e., the income distribution.

Am I right to assume that the use of CI from normal distribution theory cannot be used in explaining the non-normal distribution data?
If yes, how do I calculate the CI for the non-normal distribution data.

#3 Re: Help Me ! » Non-normal distribution.....calculating CI » 2014-04-07 13:41:08

Exact problem is I'm trying to calculate what's the range of income of 98% of the population.
The income distribution is positively skewed. 
Normally, if the data is normally distributed, I would:
1. Calculate the mean, std dev
2. use 2 std dev to find the range below the mean to find out the answer.  (that 98% of the population earns mean - 2 std dev or more)

#4 Help Me ! » Non-normal distribution.....calculating CI » 2014-04-07 13:09:33

bechau
Replies: 10

Currently I`m working with a positively skewed data.

I would like to calculate the range of values that represent x% of the data (CI).  How do I do this with skewed data?

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