Hi

I have an experiment where each subject performs 2 conditions - each having 2 levels. I also have 2 groups. I want to use 3dLME, with age as a covariate.

We want to model for diagnosis (ADHD NT), age + load (3 and 4) and direction (forward and backward).

I ran the code below and I got automatically a 3 way interaction. Using 3dLME can we also omit the 3 way interaction (diagnosis X load X direction) and only look at the 2 way interactions (diagnosis X load & diagnosis X direction & all the two-way interactions with age)?

Or would I have to write separate 3dANOVAs for direction and load)

I would be grateful for any advice!

My Code:
-model 'Dx*Direction*Number*Age' \
-ranEff '~1' \
-SS_type 3 \
-num_glt 48 \
-qVars 'Age' \
-gltLabel 1 ADHDvTD_BackvForw -gltCode 1 'Dx : 1*ADHD -1*TD Direction : -1*Forward 1*Backward' \
-gltLabel 2 ADHDvTD_4sv3s -gltCode 2 'Dx : 1*ADHD -1*TD Number : -1*Three 1*Four' \
-gltLabel 3 inForw_ADHDvTD -gltCode 3 'Direction : 1*Forward Dx : 1*ADHD -1*TD' \
-gltLabel 4 inBack_ADHDvTD -gltCode 4 'Direction : 1*Backward Dx : 1*ADHD -1*TD' \
-gltLabel 5 in4s_ADHDvTD -gltCode 5 'Number : 1*Four Dx : 1*ADHD -1*TD' \
-gltLabel 6 in3s_ADHDvTD -gltCode 6 'Number : 1*Three Dx : 1*ADHD -1*TD' \
-gltLabel 7 inForw3_ADHDvTD -gltCode 7 'Direction : 1*Forward Number : 1*Three Dx : 1*ADHD -1*TD' \
-gltLabel 8 inForw4_ADHDvTD -gltCode 8 'Direction : 1*Forward Number : 1*Four Dx : 1*ADHD -1*TD' \
-gltLabel 9 inBack3_ADHDvTD -gltCode 9 'Direction : 1*Backward Number : 1*Three Dx : 1*ADHD -1*TD' \
-gltLabel 10 inBack4_ADHDvTD -gltCode 10 'Direction : 1*Backward Number : 1*Four Dx : 1*ADHD -1*TD' \
-gltLabel 11 InForward_ADHDvTD_4sv3s -gltCode 11 'Direction : 1*Forward Number : -1*Three 1*Four Dx : 1*ADHD -1*TD' \
-gltLabel 12 InBackward_ADHDvTD_4sv3s -gltCode 12 'Direction : 1*Backward Number : -1*Three 1*Four Dx : 1*ADHD -1*TD' \
-gltLabel 13 In3s_ADHDvTD_BackvForw -gltCode 13 'Direction : -1*Forward 1*Backward Number : 1*Three Dx : 1*ADHD -1*TD' \
-gltLabel 14 In4s_ADHDvTD_BackvForw -gltCode 14 'Direction : -1*Forward 1*Backward Number : 1*Four Dx : 1*ADHD -1*TD' \
-gltLabel 15 Age_BvF -gltCode 15 'Direction : -1*Forward 1*Backward Age :' \
-gltLabel 16 Age_4v3 -gltCode 16 'Number : -1*Three 1*Four Age :' \
-gltLabel 17 Age_TD_BvF -gltCode 17 'Dx : 1*TD Direction : -1*Forward 1*Backward Age :' \
-gltLabel 18 Age_AD_BvF -gltCode 18 'Dx : 1*ADHD Direction : -1*Forward 1*Backward Age :' \
-gltLabel 19 Age_TD_4v3 -gltCode 19 'Dx : 1*TD Number : -1*Four 1*Three Age :' \
-gltLabel 20 Age_AD_4v3 -gltCode 20 'Dx : 1*ADHD Number : -1*Four 1*Three Age :' \
-gltLabel 21 InADHD_BackvForw -gltCode 21 'Dx : 1*ADHD Direction : -1*Forward 1*Backward' \
-gltLabel 22 InADHD_4sv3s -gltCode 22 'Dx : 1*ADHD Number : -1*Three 1*Four' \
-gltLabel 23 InTD_BackvForw -gltCode 23 'Dx : 1*TD Direction : -1*Forward 1*Backward' \
-gltLabel 24 InTD_4sv3s -gltCode 24 'Dx : 1*TD Number : -1*Three 1*Four' \
-gltLabel 25 InADHD_F_4v3 -gltCode 25 'Dx : 1*ADHD Direction : 1*Forward Number : -1*Three 1*Four' \
-gltLabel 26 InADHD_B_4v3 -gltCode 26 'Dx : 1*ADHD Direction : 1*Backward Number : -1*Three 1*Four' \
-gltLabel 27 InADHD_3_BvF -gltCode 27 'Dx : 1*ADHD Number : 1*Three Direction : -1*Forward 1*Backward' \
-gltLabel 28 InADHD_4_BvF -gltCode 28 'Dx : 1*ADHD Number : 1*Four Direction : -1*Forward 1*Backward' \
-gltLabel 29 InTD_F_4v3 -gltCode 29 'Dx : 1*TD Direction : 1*Forward Number : -1*Three 1*Four' \
-gltLabel 30 InTD_B_4v3 -gltCode 30 'Dx : 1*TD Direction : 1*Backward Number : -1*Three 1*Four' \
-gltLabel 31 InTD_3_BvF -gltCode 31 'Dx : 1*TD Number : 1*Three Direction : -1*Forward 1*Backward' \
-gltLabel 32 InTD_4_BvF -gltCode 32 'Dx : 1*TD Number : 1*Four Direction : -1*Forward 1*Backward' \
-gltLabel 33 InADHD_Forward -gltCode 33 'Dx : 1*ADHD Direction : 1*Forward' \
-gltLabel 34 InADHD_Backward -gltCode 34 'Dx : 1*ADHD Direction : 1*Backward' \
-gltLabel 35 InADHD_3s -gltCode 35 'Dx : 1*ADHD Number : 1*Three' \
-gltLabel 36 InADHD_4s -gltCode 36 'Dx : 1*ADHD Number : 1*Four' \
-gltLabel 37 InADHD_Forward3 -gltCode 37 'Dx : 1*ADHD Number : 1*Three Direction : 1*Forward' \
-gltLabel 38 InADHD_Forward4 -gltCode 38 'Dx : 1*ADHD Number : 1*Four Direction : 1*Forward' \
-gltLabel 39 InADHD_Backward3 -gltCode 39 'Dx : 1*ADHD Number : 1*Three Direction : 1*Backward' \
-gltLabel 40 InADHD_Backward4 -gltCode 40 'Dx : 1*ADHD Number : 1*Four Direction : 1*Backward' \
-gltLabel 41 InTD_Forward -gltCode 41 'Dx : 1*TD Direction : 1*Forward' \
-gltLabel 42 InTD_Backward -gltCode 42 'Dx : 1*TD Direction : 1*Backward' \
-gltLabel 43 InTD_3s -gltCode 43 'Dx : 1*TD Number : 1*Three' \
-gltLabel 44 InTD_4s -gltCode 44 'Dx : 1*TD Number : 1*Four' \
-gltLabel 45 InTD_Forward3 -gltCode 45 'Dx : 1*TD Number : 1*Three Direction : 1*Forward' \
-gltLabel 46 InTD_Forward4 -gltCode 46 'Dx : 1*TD Number : 1*Four Direction : 1*Forward' \
-gltLabel 47 InTD_Backward3 -gltCode 47 'Dx : 1*TD Number : 1*Three Direction : 1*Backward' \
-gltLabel 48 InTD_Backward4 -gltCode 48 'Dx : 1*TD Number : 1*Four Direction : 1*Backward' \
-dataTable \
Subj Dx Age Direction Number InputFile \
MS1049 ADHD 16 Backward Four stats.ForvBack.all2mm.instruct6s.MS1049+tlrc'[10]' \