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anne_sa
Level IV

Fit Model - Custom Test

Hello everybody,

I have a question regarding the Fit Model platform. Let's say that I am working with the Big Class data table. My Y variable is height and I have two effects in my model: age and sex.

I would like to know if the height difference between the groups 12 and 17 for M is significantly different from the height difference between the groups 12 and 17 for F. I think I can use the "Custom Test" feature but I am not sure of how to do that properly...

 

Thanks in advance!

4 REPLIES 4
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Re: Fit Model - Custom Test

Did you search the discussions for this topic first? There is a good discussion that might help you. You can find it here.

Learn it once, use it forever!
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anne_sa
Level IV

Re: Fit Model - Custom Test

Hi @markbailey 

 

Thanks this post is really helping indeed! In my example I have 3 treatments (A,B, C) and 2 Times (T0, T1) and I want to know if the difference between T1 and T0 is significantly different between the treatments.

 

If I understand correctly the first step of your post, in my situation the difference between T1 and T0 (T1-T0 = -T0-T0 = -2 T0) for the treatment A correspond to the following coefficients [0, -2, 0, 0,2,0,0]? I am not sure for the interaction term...

anne_sa_1-1596180073145.png

 

 

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Re: Fit Model - Custom Test

You can use contrasts instead of a custom test, although they are equivalent. I think that the contrast is easier to build and interpret. Set them up like this (mock up of data):

 

contrast.JPG

Learn it once, use it forever!
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anne_sa
Level IV

Re: Fit Model - Custom Test

Hi @markbailey ,

 

Thanks for your answer! If I understand correctly, in your example you test that the difference between T0 and T1 is significantly different from 0 for each treatment. So if I want to know if the gap T0-T1 is different between two treatments, I need to subtract the corresponding columns?

But I've probably missed something because I get a warning:

anne_sa_0-1596439113336.png

 

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