Discussion:
Q: SATA or other calculators may be used. Use the following data table comparing a control group to a group with paclitaxel coated angioplasty balloons implanted in leg arteries:
| Variables |
control group |
paclitaxel-coated balloons group |
| |
(n = 54) |
(n = 48) |
|
|
|
| Baseline Rutherford stage |
3.1 ± 0.8 |
|
3.4 ± 0.8 |
|
|
|
| Degree of stenosis |
91 ± 7 |
|
89 ± 8 |
|
|
|
| Target lesion length (cm) |
7.4 ± 6.7 |
|
7.5 ± 6.2 |
|
|
|
| Target lesion diameter (cm) |
4.7 ± 0.6 |
|
5.0 ± 0.7 |
|
|
|
| No. of runoff vesicles |
2.1 ± 0.8 |
|
1.8 ± 0.8 |
|
|
|
NOTE. Values are mean ± SD.
Data taken from Tepe et al. (2008) N Eng J Med. 358(7):689-699.
a. Perform the F test on all five variables listed (comparing control group to balloons group). State the p-value and conclusions that should include whether to use the equal variance approach or the unequal variance approach.
b. Perform hypothesis tests on all five variables (again comparing one group to the other). State the null hypothesis for each. List the p-value and a specific conclusion.
c. Calculate by hand the Satterthwaite's degrees of freedom for target lesion diameter (the fourth variable). Show your steps. Your answer should be the exact number that would be used in a table to look up the p-value in the subsequent hypothesis test.
d. Construct a 99% confidence interval for degree of stenosis, balloons group.