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Math Help - Chi square test

  1. #1
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    Chi square test

    According to a theory, four categories of strawberries are supposed to occur in the ratio 9:3:3:1. For these four categories, 124, 30, 43 and 11 were counted, respectively. Are these compatible with the theory?Let \alpha=0.05.

    Work so far-
    124+30+43+11=208

    Expected values are therefore 117, 39, 39, 13 for the ratio 9:3:3:1

    (4 columns - 1)=3 degrees of freedom

    I calculated the Chi-test statistic by doing (124-117)^2/117+....+(11-13)^2/13 and got 3.21, but I am not sure what to compare it to or what to do with the \alpha=0.05. Thanks for your help!
    Last edited by larz; June 26th 2009 at 02:06 PM. Reason: More work
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  2. #2
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    Quote Originally Posted by larz View Post
    According to a theory, four categories of strawberries are supposed to occur in the ratio 9:3:3:1. For these four categories, 124, 30, 43 and 11 were counted, respectively. Are these compatible with the theory?Let \alpha=0.05.

    Work so far-
    124+30+43+11=208

    Expected values are therefore 117, 39, 39, 13 for the ratio 9:3:3:1

    (4 columns - 1)=3 degrees of freedom

    I calculated the Chi-test statistic by doing (124-117)^2/117+....+(11-13)^2/13 and got 3.21, but I am not sure what to compare it to or what to do with the \alpha=0.05. Thanks for your help!
    df = 4 - 1 = 3.

    Critical value for 3 df at 0.05 significance level is 7.81 (got from tables).

    3.21 < 7.81 therefore ......
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  3. #3
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    Therefore the observations are compatible with the theory! Thanks. I found the table you are talking about. Now it makes sense.
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