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Forum Newbie
Group: Forum Members
Last Login: 3/30/2007 7:04:45 AM
Posts: 2,
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Dear e-primers, I encounters a obstacle when programming an image experiment. Three images (A,B,C) are enrolled in trial with special alignment (like AB,BA,AA,BB,CC) where 800ms duration of stimuli of each image and 400ms interval is required. so, each unit (AB,BA,AA,BB,CC) will spend 2s. I want to acquire experiment with following limits: 1. AB+BA=AA+BB=CC
AB+BA，AA+BB，CC play randomly congruence probability and also is true for AB,BA and AA,BB (AB=BA, AA=BB) 2. interval of units(AB,BA,AA,BB,CC) is randomly assign with 2s average.
After beating my heaad against the wall and read the eprime help,I don't
know how to programe the experiment and sad. Any assistance would be most appreciated!
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Forum Member
Group: Forum Members
Last Login: 4/9/2008 3:40:25 AM
Posts: 25,
Visits: 52
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As always, I am not quit shure if I am getting you right. This sounds like two challenges:
First it seems to be a question of probabilities – If it is that you want to have the probability of your trials (AB, BA …) to be equal – define them as one trial (each trial containing two pictures). Then you can select those trials from your triallist in a random fashion (whiteout replacement).
Second part of your question is: how to make a random interval for each trial – but have an average time (of two seconds) for each trial over al trials.
The solution here is: show the intertrial object (blank screen) for a random interval of 0 to 400ms. After presenting the two pictures show an additional blank screen for remaining time (so it adds up to 400ms).
‘Set the two attributes whit an inline like this:
Randomize
dim i as integer
c.SetAttrib "fixtime1", Random(0,400)
i = c.GetAttrib("fixtime1")
c.SetAttrib "fixtime2", (400 – i)
hth Patrick
Patrick
Randomization: rqube.seifseit.de
Internet: http://eeglab.uni-trier.de
or: http://britz.wordpress.com
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