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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