Randomizing Blocks

[David McFarlane]

I may not completely understand this, but will take a whack at 
it.  So you have 15 trial items, and you want to present these in a 
shuffled order across 3 blocks with 5 of these items per block.

I might start with a Structure like this:

- BlockList
     - BlockProc
         - TrialList
             - TrialItemList
             - TrialProc
                 - ...

I would set up my BlockList to run the 3 blocks of 
BlockProc.  TrialList would run 5 trials of TrialProc, pulling its 
trial items from the nested TrialItemList, which contains all 15 
trial items.  I would set TrialItemList to run in Random order (and 
make sure that it does *not* reset at beginning of each run) (also 
make sure that TrialItemList does not use any Procedure).  Now 
TrialItemList would get shuffled once, and TrialList will take one 
item from the shuffled TrialItemList for each run of TrialProc, 
automatically keeping track of where it left off and where to pick up 
again for each block.

In general, just think of Lists (whether main or nested) as decks of 
playing cards, use main Lists for running Procedures, and nested 
Lists for supplying stimulus information, etc., for each trrial.

-----
David McFarlane
E-Prime training 
online:  http://psychology.msu.edu/Workshops_Courses/eprime.aspx
Twitter:  @EPrimeMaster (https://twitter.com/EPrimeMaster )

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At 5/1/2014 02:13 PM Thursday, Natalia Hidalgo wrote:
>I am trying to create an experiment where there is a superordinate 
>list of trial items (in this case scenarios to be presented), and 
>items from this list would be pulled to be presented in three 
>blocks, so that each scenario is equally likely to be presented in 
>any of the three blocks (15 scenarios, 3 blocks, 5 trials each 
>block). I have tried nested lists but that doesn't seem to work, has 
>anybody done anything like this before?
>Thanks

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