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