Hi,

I'm trying to design a neuroimaging task in which I have 6 runs of 8
trials (2 presentations of 4 stimuli: A,B,C,D) each. I'm setting up my
design matrix using excel, with runs in six columns and trials in eight
rows.

In my first column, I need to constrain the first two rows to either A
or B.  Other than this, I'd like to randomly present two of each item
in each column.  I was going to stop here, and just use a RAND function
to pair with and sort each of the 6 columns.  However, I just learned
that I need to also take into account possible order effects, and make
sure that across the columns, I make sure each condition appears at
least once. I have NO idea how to set up a function in excel that can
ensure both of these parameters... Does anyone have any idea how to do
this?  I've tried to search across this forum, but I'm having a hard
time finding it with proper search terms.

Thank you for any help you can offer!

Lauren

PS. I also have access to matlab, if that would help me at all...