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 ?2>________
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 ?2.
?2= ________
Based on comparing the computed ?2 to the rejection level ?2 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.