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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
Sample Size Determination for Outcomes from Two-Level Trials 169
The corresponding statistical power can be expressed as
ϕ
xz(2)
= Φ
(
XZ(2)
r
N
(0,0)
2
N
1
.
4f Φ
1
(1 α/2)
)
.
where
XZ(2)
=
δ
XZ(2)
σ
. Accordingly, the corresponding required sample
size is [16]:
N
(0,0)
2
=
4fz
2
α,φ
N
1
2
XZ(2)
. (5.26)
It is notable that when Equations (5.5) and (5.26) are compared, it is
clear that N
(0,0)
2
= 2N
(0)
2
, where N
(0)
2
is the required sample size for the
control arm (X = 0) for testing H
0
: δ
(2)
= 0 in model (5.3). If follows that
the total number of measurements, that is, 4N
(0,0)
2
N
1
required for testing
H
0
: δ
XZ(2)
= 0 in model (5.25) is four times larger than the total number
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Publisher Resources

ISBN: 9781466556270