3dttest++ VS 3dDecon comparisons


I am interested in comparing two different stimuli classes wordsVhouses and found that when I look at the output for when I have 3dDeconvolve do the comparison and the output for when I do a two sided t-test in ttest++ they are different. 

In the first case I compared wordsVhouses as a GLT in my 3dDecon script and then put that subbrick into 3dttest++ as a one sided t-test. In the second case I took the subbrick for words and the subbrick for houses and compared the two in ttest++. The results are similar, but the 3dDecon is noisier and I am wondering why that is, should these be doing something very similar?

Thank you for your help!

The two approaches should render virtually the same result except for rounding errors. In addition, the issue of one- vs. two-sided testing is not relevant; that should be the case at least in AFNI as well as in statistics in general except that some software packages may have a peculiar setup.

Be sure you are doing a paired test.

  • rick

That was the issue… I had left off the -paired option, ugh such a little thing can cause so much grief! Thank you so much!