Practice Problems

1. The following data was collected in a clinical trial evaluating a new compound designed to improve wound healing in trauma patients. The new compound was compared against a placebo. After treatment for 5 days with the new compound or placebo the extent of wound healing was 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.

Step 1. Set up hypotheses and determine level of significance.

H₀:

H₁: a=0.05

Step 2. Select the appropriate test statistic.

Step 3. Set up decision rule.

Step 4. Compute the test statistic.

Step 5. Conclusion.

(b) Use the data in Problem #1 and pool the data across the treatments into one sample of size n=250. Use the pooled data to test whether the distribution of the percent wound healing is approximately normal. Specifically, use the following distribution: 30%, 40%, 20% and 10% and a=0.05 to run the appropriate test.