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Math Help - Stats Question

  1. #1
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    Apr 2009
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    Stats Question

    Hi guys,


    I did part a of this question.Not sure if its right though
    Can some please explain part b?




    4. Two traits which have been studied extensively in tomato plants are height (tall vs. dwarf) and
    leaf type (cut vs. potato). In a particular breeding experiment, 1611 tomato plants were grown and
    classified by leaf type and height. The results are given below

    Leaf Type
    Cut Potato Total
    Tall 926 288 1214
    Height Dwarf 293 104 397
    Total 1219 392 1611


    (a) A genetic theory predicts that leaf type and height are independent. Perform a chi-square test of independence for the hypothesis implied by this genetic theory by completing the following work:
    i. List H0 and Ha.
    H0 : p1 =p2 and Ha: p1 not equal to p2
    ii. Find the expected value under H0 for each observation in the table.
    E(11) = (1214 x 1219)/1611 = 918.6
    E(12) = (1214 x 392)/1611 = 295.4
    E(21) = (397 x 1219)/1611 = 300.4
    E(22) = (397 x 392)/1611 = 96.6

    iii. Calculate the chi-square test statistic and specify its degrees of freedom.
    Chi-Sq = (((926-918.6)^2)/918.6) + (((288-295.4)^2)/295.4) + (((293-300.4)^2)/300.4) + (((104-96.6)^2)/96.6)
    = 0.06 + 0.185 + 0.182 + 0.567
    = 0.994

    d.f. = either 3 or 1?

    iv. Find the range of the p-value of the test.

    0.319

    v. Draw a conclusion of the test based on the significance level 0.05.

    0.319>0.05
    Therefore we accept the null hypothesis

    (b) A more detailed theory predicts that the 4 types of tomato plant given above appear in a
    9:3:3:1 (tall cut : tall potato : dwarf cut : dwarf potato) ratio. Perform a chi-square goodness
    of fit test to check whether the data support this theory or not.
    i. List H0 and Ha.
    ii. Find the expected value under H0 for each observation in the table.
    iii. Calculate the chi-square test statistic and specify its degrees of freedom.
    iv. Find the rejection region of the test at the significance level 0.05.
    v. Draw a conclusion of the test based on the sig
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  2. #2
    Newbie
    Joined
    Apr 2009
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    For (b) A more detailed theory predicts that the 4 types of tomato plant given above appear in a
    9:3:3:1 (tall cut : tall potato : dwarf cut : dwarf potato) ratio. Perform a chi-square goodness
    of fit test to check whether the data support this theory or not.
    i. List Ho and Ha.

    Ho: p1= 0.5625, p2= 0.1875, p3= 0.1875 and p4= 0.0625
    H1: not all p1 are as specified in Ho

    ii. Find the expected value under Ho for each observation in the table.

    E(11) = 0.5625 x 1611 = 906.19
    E(12) = 0.1875 x 1611 = 302.06
    E(21) = 0.1875 x 1611 = 302.06
    E(22) = 0.0625 x 1611 = 100.69


    iii. Calculate the chi-square test statistic and specify its degrees of freedom.
    Chi-Sq = (((926-906.19)^2)/906.19) + (((288-302.06)^2)/302.06) + (((293-302.06)^2)/302.06) + (((104-100.69)^2)/100.69)
    = 0.433 + 0.654 + 0.272 + 0.11
    = 1.469

    d.f. = 4-1
    = 3
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