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    Some Applications of Chi-Square Test

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    I need to know which equation to use and detailed steps to answer the following question by hand.

    The following data were collected in a clinical trial evaluating a new compound designed to improve wound healing in trauma patients. The new compound is compared against a placebo. After treatment for 5 days with the new compound or placebo the extent of wound healing is measured and the data are shown below.

    Percent Wound Healing
    Treatment 0-25% 26-50% 51-75% 76-100%
    New Compound (n=125) 15 37 32 41
    Placebo (n=125) 36 45 34 10

    Is there a difference in the extent of wound healing by treatment? (Hint: Are treatment and the percent wound healing independent?) Run the appropriate test at a 5% level of significance.
    df= _____
    alpha= ________
    Reject H0 if χ2> ________
    Z =

    Compute expected frequencies
    Expected Frequency = (Row Total * Column Total)/N.

    Complete the expected frequencies for each cell.

    Percent Wound Healing Total
    Treatment 0-25% 26-50% 51-75% 76-100%
    New Compound 15
    ( ) 37
    ( ) 32
    ( ) 41
    ( ) 125
    Placebo 36
    ( ) 45
    ( ) 34
    ( ) 10
    ( ) 125
    Total 51 82 66 51 250

    Compute χ2.
    χ2= ________

    Based on comparing the computed χ2 to the rejection level χ2 which of the following is (are) true?
    A. We have statistically significant evidence at alpha=0.05 to show that H0 is false.
    B. Treatment and percent wound healing are not independent.
    C. Treatment and percent wound healing are independent.
    D. a and b.

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    Solution Summary

    The solution gives detailed steps on performing a chi-square test for checking independence for multiple groups. Also, another chi-square test using expected frequency technique is shown and explained.