hpow in ETAC

AFNI Message Board
1

I am new to using ETAC in 3dttest++ and I have a question about the hpow value. In a dataset I’m currently analyzing, when hpow is set to 0, I get cluster activity that makes sense and is in line with what -Clustsim in 3dttest++ gives me, but when hpow is set to 1 or 2, no voxels pass the correction. Could someone help me to wrap my head around what that means? I’ve pasted my full 3dttest++ command below and I’d appreciate any insight into how to interpret this.

Thanks in advance!

3dttest++ -setA Int
sub001 stats.sb21730_REML+tlrc.‘[44]’
sub002 stats.sb21750_REML+tlrc.‘[44]’
sub003 stats.sb21767_REML+tlrc.‘[44]’
sub004 stats.sb21824_REML+tlrc.‘[44]’
sub005 stats.sb21826_REML+tlrc.‘[44]’
sub006 stats.sb21827_REML+tlrc.‘[44]’
sub007 stats.sb21838_REML+tlrc.‘[44]’
sub008 stats.sb21840_REML+tlrc.‘[44]’
sub009 stats.sb21843_REML+tlrc.‘[44]’
sub010 stats.sb21847_REML+tlrc.‘[44]’
sub011 stats.sb21858_REML+tlrc.‘[44]’
sub012 stats.sb21862_REML+tlrc.‘[44]’
sub013 stats.sb21866_REML+tlrc.‘[44]’
sub014 stats.sb21873_REML+tlrc.‘[44]’
sub015 stats.sb21875_REML+tlrc.‘[44]’
sub016 stats.sb21876_REML+tlrc.‘[44]’
sub017 stats.sb21878_REML+tlrc.‘[44]’
sub018 stats.sb21889_REML+tlrc.‘[44]’
sub019 stats.sb22100_REML+tlrc.‘[44]’
sub020 stats.sb22104_REML+tlrc.‘[44]’
sub021 stats.sb22115_REML+tlrc.‘[44]’
sub022 stats.sb22122_REML+tlrc.‘[44]’
sub023 stats.sb22135_REML+tlrc.‘[44]’
sub024 stats.sb22144_REML+tlrc.‘[44]’
-prefix Int_Allhs -Etac -ETAC_opt NN=2:sid=2:hpow=0,2:pthr=0.01/0.001/19:name=hpow0:fpr=5 -ETAC_opt NN=2:sid=2:hpow=2,2:pthr=0.01/0.001/19:name=hpow2:fpr=5 -ETAC_opt NN=2:sid=2:hpow=2,2:pthr=0.01/0.001/19:name=hpow1:fpr=5 -mask group_mask+tlrc.HEAD

2

I’m sorry for the double post. I just noticed a mistake I was making, but I’m still a bit confused. My 3dttest++ command above should have been the version I’ve pasted below. When I fixed this, I now have no voxels that pass the correction for hpow=0, hpow=1, or hpow=2 when tested separately. However, when I run -ETAC_opt NN=2:sid=2:hpow=0,1,2:pthr=0.01/0.001/19:name=all:fpr=5 I get clusters that pass the correction. The help page says there is little reason for including all three hpows in a single call. Could you please explain that more? Thanks again and I’m sorry for the confusion!

3dttest++ -setA Int
sub001 stats.sb21730_REML+tlrc.‘[44]’
sub002 stats.sb21750_REML+tlrc.‘[44]’
sub003 stats.sb21767_REML+tlrc.‘[44]’
sub004 stats.sb21824_REML+tlrc.‘[44]’
sub005 stats.sb21826_REML+tlrc.‘[44]’
sub006 stats.sb21827_REML+tlrc.‘[44]’
sub007 stats.sb21838_REML+tlrc.‘[44]’
sub008 stats.sb21840_REML+tlrc.‘[44]’
sub009 stats.sb21843_REML+tlrc.‘[44]’
sub010 stats.sb21847_REML+tlrc.‘[44]’
sub011 stats.sb21858_REML+tlrc.‘[44]’
sub012 stats.sb21862_REML+tlrc.‘[44]’
sub013 stats.sb21866_REML+tlrc.‘[44]’
sub014 stats.sb21873_REML+tlrc.‘[44]’
sub015 stats.sb21875_REML+tlrc.‘[44]’
sub016 stats.sb21876_REML+tlrc.‘[44]’
sub017 stats.sb21878_REML+tlrc.‘[44]’
sub018 stats.sb21889_REML+tlrc.‘[44]’
sub019 stats.sb22100_REML+tlrc.‘[44]’
sub020 stats.sb22104_REML+tlrc.‘[44]’
sub021 stats.sb22115_REML+tlrc.‘[44]’
sub022 stats.sb22122_REML+tlrc.‘[44]’
sub023 stats.sb22135_REML+tlrc.‘[44]’
sub024 stats.sb22144_REML+tlrc.‘[44]’
-prefix Int_CorrectedTogether -Etac -ETAC_opt NN=2:sid=2:hpow=0:pthr=0.01/0.001/19:name=h0:fpr=5 -ETAC_opt NN=2:sid=2:hpow=1:pthr=0.01/0.001/19:name=h1:fpr=5 -ETAC_opt NN=2:sid=2:hpow=2:pthr=0.01/0.001/19:name=h2:fpr=5 -mask group_mask+tlrc.HEAD

3

I never received a response to this question and I’m still really confused about how to interpret the results. When I use a single hpow value in ETAC (0,1, or 2) for some contrasts, I do not get any significant clusters. However, when I use a combination of hpow values as in the command below, I do get significant voxels.


-ETAC_opt NN=2:sid=2:hpow=0,2:pthr=0.01/0.001/19:name=h1:fpr=5 -ETAC_opt NN=2:sid=2:hpow=2:pthr=0.01/0.001/19:name=h2:fpr=5

I’ve read the Etac paper and I can’t wrap my head around why adding more comparisons (additional hpow values) would make some voxels pass the test when there were none that passed the test with a single hpow. I would greatly appreciate any help!