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[Statistics] Obtaining test statistic in short problem

  1. Jun 26, 2012 #1
    Hey everyone! Exam practice, that time of year. In this problem 13 with correct answer C, I'm not sure how they get the test statistic: http://i.imgur.com/doar3.jpg


    I think they want you to use a F-test, that tests the entire model, which is calculated by: F= ((R^2)/ K)/ ((1 - R^2)/(n-K-1)) where K is the number of independent variables (3 in this question)

    Then the R square is the percentage of the model that is explained, so the explained variation in Y / total variation in Y

    R^2 = SSR / (SSE+SSR)
    SSR= sum of squared regression, SSE=sum of squared errors

    Thanks for any help or insight!
    Many thanks
     
  2. jcsd
  3. Jun 27, 2012 #2
    I think they are doing a contingency table with a chi-square statistic.
     
  4. Jun 28, 2012 #3
    Right, but I'm still at a loss! :)
     
  5. Jun 28, 2012 #4
    Well, how many people in each of the three categories would expect, based on the predicted percentages? And how many were actually surveyed?
     
  6. Jun 29, 2012 #5
    Hey, thanks for helping!

    It's a sample of 120 people, so n=120
    So in this sample : 60 workers, 30 students, 30 retirees
     
  7. Jul 5, 2012 #6

    Ray Vickson

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    Science Advisor
    Homework Helper

    That was not the question. The question was: how many would you EXPECT in each group if the predicted percentages held true?

    RGV
     
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