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Easy Skewness question

  1. Jun 9, 2014 #1

    joshmccraney

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    hey pf!

    i am wondering, if you're looking at two data sets and each set has different skewness levels (i.e. perhaps set 1 has a skewness of .4 and set 2 has a skewness of .5) do we say that these two are relatively un-skewed or highly skewed (or perhaps one of each)?

    in other words, how do i compare levels of skewness?

    i have the same question for kurtosis, if you could explain?

    thanks a ton!

    josh
     
  2. jcsd
  3. Jun 9, 2014 #2

    FactChecker

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    You may be trying to get more out of these measurements than they deserve, but that's OK. Here is my two bits. Maybe someone can clarify more:

    The skewness of a PDF is definitely influenced by its standard deviation, σ. For this reason, I think that the skew values of two PDFs can only be meaningfully compared if they have identical standard deviations. Of course, any symmetric PDF will have skewness=0. Other than that, I would normalize the skewness number by dividing it by σ3. I would look at some well known unsymmetric distributions like Chi2 and normalize their skewness values to get a feel for the meaning of some values. I have never done this exercise, but maybe someone else can add some insight.
     
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