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Sample Size Calculations for Clustered and Longitudinal Outcomes in Clinical Research
book

Sample Size Calculations for Clustered and Longitudinal Outcomes in Clinical Research

by Chul Ahn, Moonseoung Heo, Song Zhang
December 2014
Intermediate to advanced content levelIntermediate to advanced
260 pages
8h 51m
English
Chapman and Hall/CRC
Content preview from Sample Size Calculations for Clustered and Longitudinal Outcomes in Clinical Research
108 Sample Size Calculations for Clustered and Longitudinal Outcomes
For the CS correlation structure, a consistent estimator of ρ can be obtained
by
ˆρ =
2
P
n
i=1
P
m1
j=1
P
m
j
0
=j+1
ˆ
ij
ˆ
ij
0
ˆσ
2
nm(m 1)
.
For the AR(1) correlation structure, the consistent estimator of ρ can be
obtained from the equation
n
X
i=1
m1
X
j=1
m
X
j
0
=j+1
ˆ
ij
ˆ
ij
0
ˆσ
2
ρ
|t
ij
t
ij
0
|
= 0.
Suppose we apply the GEE sample size method to a labor pain study
[36]. Eighty-three women in labor were randomly assigned to either receive
a pain medication (43 women) or a placebo (40 women). Self-reported pain
scores were collected at 30-minute intervals, with 0 indicating no pain and
100 indicating extreme ...
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Publisher Resources

ISBN: 9781466556270