AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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Craig Stark
March 26, 2003 09:19AM
> -expr
> 'a*step(step(b)+step(c)+step(d)+step(e)+step(f)+step(g)+step(h))'
> where a=the f stat and b-h are the COEFS for each of the
> individual conditions that i would like to include.

Well, a>0 and all those steps make sure that what's to the right will be >0, so that's why you're only getting positive values. If you did something like:

a * ( (2*step(b)-1) * (2*step(c)-1) * ... (2*step(h)-1) )

I think you'll have what you were trying to get at -- the combined sign of all of the effects. Whether it makes sense statistically may be another story. Out of curiosity, if you just have these conditions, why not use the overall model's F? Also, if you have just these conditions and you want to see whether a region is active or "deactivated" -- relative to what?

Craig
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Subject Author Posted

how do i get a signed f stat ?

carl March 25, 2003 06:11PM

Re: how do i get a signed f stat ?

Craig Stark March 26, 2003 09:19AM

Re: how do i get a signed f stat ?

Ziad March 26, 2003 11:04AM