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Thread: How to randomly select 6 sets of trials and randomize them afterwards. (case 27392)

  1. #1
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    How to randomly select 6 sets of trials and randomize them afterwards. (case 27392)

    In my expriment, I want to randomly select 6 sets of 8 trials to be presented (48 trials in total) from a pool of 256 trials. Is it possible to select these 48 trials and then randomly present them on screen?

    I've attached the file I'm using to create the experiment for reference.
    Attached Files Attached Files
    Last edited by jason_reed; 07-10-2017 at 10:10 AM.

  2. #2
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    For your file named Exp 2.cv, insert a row after trial 48 in the block (e.g., right after row 50). Use a value of 0 in the wgr cell of this new row. This will make DirectRT present only 48 trials randomly selected from the ones in your .csv input file with the same number in the wgr cells.

    To ensure that only 48 trials are presented, use the skip feature of DirectRT in this same row (see http://www.empirisoft.com/directrt/h...t_skipping.htm). Skip to the trial that follows the last of the possible 256 trials (i.e., row 259 of the Exp 2.csv file). I would also recommend using unique numbers in the trial cell of all the rows of your .csv input file to avoid possible confusion.
    Jason Reed
    Empirisoft Software Support Specialist

  3. #3
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    Quote Originally Posted by jason_reed View Post
    For your file named Exp 2.cv, insert a row after trial 48 in the block (e.g., right after row 50). Use a value of 0 in the wgr cell of this new row. This will make DirectRT present only 48 trials randomly selected from the ones in your .csv input file with the same number in the wgr cells.

    To ensure that only 48 trials are presented, use the skip feature of DirectRT in this same row (see http://www.empirisoft.com/directrt/h...t_skipping.htm). Skip to the trial that follows the last of the possible 256 trials (i.e., row 259 of the Exp 2.csv file). I would also recommend using unique numbers in the trial cell of all the rows of your .csv input file to avoid possible confusion.
    Thank you so much for your response. This solves one huge piece of the puzzle. However, I am still unsure how to randomly select 6 groups out of the 32. Using the attached excel sheet as a reference, I was hoping to find a way to randomly select 6 sets, as grouped in column "I".

    Correct me if I'm wrong, but I don't think I can assign these groups their own "rbg" values and then follow your suggested method to solve this.

  4. #4
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    Quote Originally Posted by jason_reed View Post
    For your file named Exp 2.cv, insert a row after trial 48 in the block (e.g., right after row 50). Use a value of 0 in the wgr cell of this new row. This will make DirectRT present only 48 trials randomly selected from the ones in your .csv input file with the same number in the wgr cells.

    To ensure that only 48 trials are presented, use the skip feature of DirectRT in this same row (see http://www.empirisoft.com/directrt/h...t_skipping.htm). Skip to the trial that follows the last of the possible 256 trials (i.e., row 259 of the Exp 2.csv file). I would also recommend using unique numbers in the trial cell of all the rows of your .csv input file to avoid possible confusion.
    Thank you for your response. This solves a big part of the problem. However, correct me if I'm wrong , I don't think this solves my issue entirely. Using the attached excel sheet as a reference, I would like to randomly select 6 sets of trials as grouped in column "I", and then randomize them again. I don't think I can simply do this by assigning each set its unique rbg number, in addition to your suggestion.

    Also, to your last point, are you referring to the "instructions" rows?

  5. #5
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    Quote Originally Posted by jason_reed View Post
    For your file named Exp 2.cv, insert a row after trial 48 in the block (e.g., right after row 50). Use a value of 0 in the wgr cell of this new row. This will make DirectRT present only 48 trials randomly selected from the ones in your .csv input file with the same number in the wgr cells.

    To ensure that only 48 trials are presented, use the skip feature of DirectRT in this same row (see http://www.empirisoft.com/directrt/h...t_skipping.htm). Skip to the trial that follows the last of the possible 256 trials (i.e., row 259 of the Exp 2.csv file). I would also recommend using unique numbers in the trial cell of all the rows of your .csv input file to avoid possible confusion.
    Thank you for the response, this was incredibly useful. However, is it possible to randomly select a number of blocks of trials and then in essence combine them into one big block of trials to randomize them once more?

  6. #6
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    I'm glad that this has been helpful. In regards to your last response, is it necessary to randomize twice? Randomization of elements two times does not make the elements "more random" after a first round of randomization.
    Jason Reed
    Empirisoft Software Support Specialist

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