Discussion:
Q: 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.
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.
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.