1. You are a nurse in a clinic that treats patients with spinal cord injuries. You have been asked to investigate wheelchair maneuvering in patients with lower-level spinal cord injury (SCI) compared to healthy controls. During static sitting conditions, average pressures were recorded under the ischial tuberosities (bottom part of pelvic bones). The data for measurements of the left ishchial tuberosity (in mm HG) for the SCI and controls is provided in the table below. It is known that pressure measurements in both populations are normally distributed with equal variances. Can we conclude, on the basis of these data that, in general, healthy subjects exhibit lower pressure than SCI subjects? Assume α = 0.05, state the hypothesis that you are testing and show all calculations (you can use SPSS to check your numbers and to produce any graphical displays).
Pressures (mm Hg) Under the Pelvis during Static Conditions in 10 Subjects
|
Subject #
|
SCI
|
Control
|
|
1
|
60
|
131
|
|
2
|
150
|
115
|
|
3
|
130
|
124
|
|
4
|
180
|
131
|
|
5
|
163
|
122
|
|
6
|
130
|
117
|
|
7
|
121
|
88
|
|
8
|
119
|
114
|
|
9
|
130
|
150
|
|
10
|
148
|
169
|
2. You are interested in whether the data you have collected provide sufficient evidence to indicate a difference in mean serum uric acid levels between normal individuals and individuals with Down's syndrome. The data consist of serum uric acid readings on 12 individuals with Down's syndrome and 15 normal individuals. The means are 4.5 mg/100 ml for the Down's sample and 3.4 mg/100 ml for the sample of normal individuals. Assume that the two independent samples are drawn from normally distributed populations with variances equal to 1 and 1.5 for the Down's and normal samples, respectively. Do you have sufficient evidence to indicate a difference in uric acid levels? Assume α = 0.05, state the hypothesis that you are testing, show all calculations, provide the p value for the test statistic, and provide the 95% confidence interval for the difference between the two means.
3. Some researchers have observed a greater airway resistance in smokers than in nonsmokers. Suppose a study, conducted to compare the percent of tracheobronchial retention of particles in smoking-discordant monozygotic twins, yielded the results in the table below for 12 pairs of twins. Do these data support the hypothesis that tracheobronchial clearance is slower in smokers? Assume α = 0.05 and differences in the two populations are normally distributed. State the hypothesis that you are testing, show all calculations, and provide a p-value for the statistical test you conduct. You can use SPSS to check your numbers and produce any graphs.
|
% Retention - Smoking Twin
|
% Retention - Nonsmoking Twin
|
|
60.6
|
47.5
|
|
12.0
|
13.3
|
|
56.0
|
33.0
|
|
75.2
|
55.2
|
|
12.5
|
21.9
|
|
29.7
|
27.9
|
|
57.2
|
54.3
|
|
62.7
|
13.9
|
|
28.7
|
8.9
|
|
66.0
|
46.1
|
|
25.2
|
29.8
|
|
40.1
|
36.2
|