Re: [Freesurfer] repeated measures ANOVA 2x2 covariate

[Douglas N. Greve]

See https://surfer.nmr.mgh.harvard.edu/fswiki/PairedAnalysis

On 3/28/2022 3:18 AM, Agurne Sampedro Calvete wrote:


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Dear Douglas,

Do you mean calculate a type of change score (e.g. time2 minus time1) 
and then compare the differences between the two groups? How can I 
calculate the difference between the two time points?

Thank you very much.

Best regards,

Agurne





El dom, 27 mar 2022 a las 23:07, Douglas N. Greve 
() escribió:


Probably the easiest thing to do since you have only two time
points is to compute the difference between the two, then just do
a simple group analysis where you include the covariates that you
want.

On 3/23/2022 10:00 AM, Agurne Sampedro Calvete wrote:


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Dear FreeSurfer experts,

I am doing a repeated measures ANOVA 2x2 (2 groups and 2 time
points) and I would like to include in the analysis a covariate
that is constant over the 2 times (e.g., baseline medication).
I would like to see a "group x time x covariate" interaction.

What should the design look like? I know that without covariate
the design is as follows:


GroupDescriptorFile 1

Class Subject1

Class Subject2

Variables    Tp1vsTp2.Group1   Tp1vsTp2.Grroup2

Input  Subject1_time1  Subject1
1 0

Input  Subject1_time2  Subject1 -1 0

Input   Subject2_time1  Subject2 0 1

Input  Subject2_time2  Subject02  0 -1

Design matrix:

1 0 1 0

1 0 -1 0

0 1 0 1

0 1 0 -1


Contrasts (.mtx files):
Tp1vsTp2.Group1        0 0 1 0
Tp1vsTp2.Group2        0 0 0 -1
Interaction (timexgroup) 0 0 1 -1


However, I do not know how I could include the interaction with
that covariate.

Thank you very much in advance.

Kind regards,

Agurne



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Re: [Freesurfer] repeated measures ANOVA 2x2 covariate

[Douglas N. Greve]

Probably the easiest thing to do since you have only two time points is 
to compute the difference between the two, then just do a simple group 
analysis where you include the covariates that you want.


On 3/23/2022 10:00 AM, Agurne Sampedro Calvete wrote:


External Email - Use Caution

Dear FreeSurfer experts,

I am doing a repeated measures ANOVA 2x2 (2 groups and 2 time points) 
and I would like to include in the analysis a covariate that is 
constant over the 2 times (e.g., baseline medication).

I would like to see a "group x time x covariate" interaction.

What should the design look like? I know that without covariate the 
design is as follows:


GroupDescriptorFile 1

Class Subject1

Class Subject2

Variables    Tp1vsTp2.Group1   Tp1vsTp2.Grroup2

Input   Subject1_time1  Subject1 1 0

Input   Subject1_time2  Subject1 -1    0

Input   Subject2_time1  Subject2 0 1

Input   Subject2_time2  Subject02  0 -1

Design matrix:

1 0 1 0

1 0 -1 0

0 1 0 1

0 1 0 -1


Contrasts (.mtx files):
Tp1vsTp2.Group1        0 0 1 0
Tp1vsTp2.Group2        0 0 0 -1
Interaction (timexgroup) 0 0 1 -1


However, I do not know how I could include the interaction with that 
covariate.


Thank you very much in advance.

Kind regards,

Agurne



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