[R] Sample size of longitudinal and skewed data

From: Lao Meng <laomeng.3_at_gmail.com>
Date: Mon, 21 Mar 2011 15:19:45 +0800

Hi all:
I have a question about the sample size calculation.

It's a pilot study,which includes 2 groups(low,high),3 time point(3,6,9 monthes).Each person has 3 results which according to the

3 time points.So it's a longitudinal study.

I want to calculate the minimum sample size from the pilot study, but can't find the solution since the data is highly skewed and

it's a longitudinal study or multi-level model,which can't use common algorithm.

Any suggestions from you are welcome.

The demo data is as follow:

id group time result

a low       3      0
a low      6       0
a low      9      3
b low     3       0
b low     6     0
b low     9     5
c high   3     0

c high 6 10
c high 9 80
d high 3 50
d high 6 65
d high 9 100
... ...

Thanks for your help.

My best.

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