random assignment of stimulus to condition while keeping the assignment fixed throughout the experiment?

[David McFarlane]

Regina,

Stock reminder:  1) I do not work for PST.  2) PST's trained staff 
takes any and all questions at 
http://support.pstnet.com/e%2Dprime/support/login.asp , and they 
strive to respond to all requests in 24-48 hours (although current 
estimates are more like 10 days) -- this is pretty much their 
substitute for proper documentation, so make full use of it.  3) If 
you do get an answer from PST Web Support, please extend the courtesy 
of posting their reply back here for the sake of others.

That said, here is my take...

Offhand, this sounds like the same issue faced in Study/Recall 
designs, and PST helpfully provides an example that you may download 
from the Samples area of their web site (though I don't know how good 
it is -- the PST examples have the virtue that they usually do 
provide bona fide working models, but PST programmers are generally 
sloppy and provide poor models to follow).  In short, you almost 
certainly have to use inline code to construct a List (or better yet, 
nested List) during the first phase for use in later phases of the run.

-- David McFarlane, Professional Faultfinder


>Dear e-prime experts,
>
>I'm having a seemingly simple issue where your thoughts would be much
>appreciated:
>
>I have a set of stimuli (eg, snakes), half of which I want to randomly
>assign to condition A, and the other half to condition B (for a given
>participant; condition here refers to presentation type).
>If I were presenting each stimulus only once, this would be easy to
>accomplish (e.g., by simply nesting a list of all the snake stimuli -
>where selection is random without replacement- in both a list of
>condition A and in a list of condition B).
>
>However, I'd like to present each stimulus twice to a given
>participant-- so, if e.g., "snake1.bmp" got assigned to the condition
>A, I would like to present it one more time during the experiment,
>again in condition A.
>
>I am having trouble figuring out how to accommodate these needs in an
>eprime list format. In other words, I would like to be able to
>generate the random assignment of stimulus to condition, and to use
>this assignment information more than once during the experiment
>(i.e., twice).
>
>Thank you very much in advance for your thoughts!
>
>Regina

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