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Some Applications of Chi-Square Test

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.

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.

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