Left ventricular mass (LVM) is an important risk factor for subsequent cardiovascular disease. A study is proposed to assess the relationship between childhood blood-pressure levels and LVM in children as determined from echocardiograms. The goal is to stratify children into a normal bp group (< 80th percentile for their age, gender, and height) and an elevated bp group (≥ 90th percentile for their age, gender, and height) and compare change in LVM between the two groups. Before this can be done, one needs to demonstrate that LVM actually changes in children over a 4-year period. To help plan the main study, a pilot study is conducted where echocardiograms are obtained from 10 random child
Left ventricular mass (LVM) is an important risk factor for subsequent cardiovascular disease. A study is proposed to assess the relationship between childhood blood-pressure levels and LVM in children as determined from echocardiograms. The goal is to stratify children into a normal bp group (< 80th percentile for their age, gender, and height) and an elevated bp group (≥ 90th percentile for their age, gender, and height) and compare change in LVM between the two groups. Before this can be done, one needs to demonstrate that LVM actually changes in children over a 4-year period.
To help plan the main study, a pilot study is conducted where echocardiograms are obtained from 10 random children from the Bogalusa Heart Study at baseline and after 4 years of follow-up. The data are given in Table 9.18.
A)Suppose the investigators are reluctant to assume that the change in LVM over four years is
B)What are the hypotheses being tested with this test?
C) What is the test statistic for this test as applied to the data in Table 9.18?
Hint: Assume that the large sample method of significance testing is valid for these data, despite the n = 10.
D) What is the critical region at the 5% level? (i.e., for what values of the test statistic will we reject H0 at the 5% level?)
E)What is the two-sided p-value for this test?
F) Now perform the test using the exact method and obtain a 2-sided p-value.
G)Compare your results in Problems E and F.
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