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Help involving Chi squared test!

  1. May 2, 2009 #1
    URGENT help involving Chi squared test!

    Hello, I am doing a chi squared test for a project due soon and everything is fine, except for one thing....for one of my rows the expected value is zero!...and the equation is (O-E)^2/E...but I can't divide it by zero because that will give infinity...so what do I do if the expected value is zero? not include it in the summation?.....

    Help is greatly appreciated!
     
  2. jcsd
  3. May 2, 2009 #2

    statdad

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    Re: URGENT help involving Chi squared test!

    A common suggestion is to combine cells for which the expected count is below 5: pool cells until every cell has expected count >=5, then do the test. when you do this base the degrees of freedom on the number of cells after combination, not the original number.

    you could also try a different test.
     
  4. May 2, 2009 #3
    Re: URGENT help involving Chi squared test!

    Hm I'm not quite sure I follow, I am just suppose to combine rows together? I don't think that would work in my case, and my expected values for any given row are low anyway....is there something else I can do?....I don't think there is an alternate test, at least not that we have been tought.
     
  5. May 17, 2009 #4
    Re: URGENT help involving Chi squared test!

    unless one row total or column total is exactly 0, then the expected cannot be 0. is the expected calculated right?

    expected=[row total]x[column total]/[table total]

    if one of the totals indeed 0, then the category containing that is completely invalid!
     
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