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 echocar-diograms. 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 2 groups. Before this can be done, one needs to dem-onstrate 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 7.6.
Since this was a pilot study, the main question of interest is how many subjects would be needed to detect an increase of 10 g in
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Fundamentals of Biostatistics
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