> It turns out that 3dRegAna does not care about the specific numbers that are used to code
> conditions and seems to care only about the spacing between the numbers.

Yes, that's expected. The only difference among different equally-spaced coding would be on the intercept, which you're probably not interested.

> Does this mean that our earlier analyses looking for linear trends across the three
> conditions were actually not equivalent to t-tests between the first and third condition?

Right, your approach with 3dRegAna is legitimate and is something I've been thinking of implementing it into 3dLME. The contrast between the first and third condition would *not* properly detect the linear trend.

> are our earlier test for linear increases using 3dRegAna still valid?

Yes, they are as solid as a rock.

Gang



Edited 1 time(s). Last edit at 04/09/2014 03:29PM by Gang.