Question

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_>________

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?

1. We have statistically significant evidence at alpha=0.05 to show that H₀ is false.
2. Treatment and percent wound healing are not independent.
3. Treatment and percent wound healing are independent.
4. a and b.

Answer 1

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