Randomization condition

Dear all,

I made a n-back task, and for each part of the task (1back 2back 3back) I created a sequential loop that randomizes the letter that comes next. Using code, the task then registers whether the letter was a n-back (was the same as the letter as n times before) and whether the participant clicked correctly. This all works all.

However, I would like to control the % of n-back present in the task. So, now there is a lot of variation, in some participants 10% of the trials is a n-back, in others 20. If possible I would like to make this around 33% for everyone (so: in within the randomization I wanted that 33% of the letters become a n-back (i.e., the same letter as n times before)) and thus keep it equal. I only have no idea where to start, and how to do this.

Best regards, Sanne Bruijniks

You could do this easily by generating the full sequence for a participant at the start of the session. Start by randomly generating the full sequence, then counting the number of n-backs you have, and then choose a number of random positions to change the letter to achieve the number you need.

Dear SDAMcIntyre,

mm thank you, that make senseā€¦ But how would you do this? Would this be possible in the Coder? Because this needs to be generated in the excel file (column with letters) then, that I now use in a random loop

Best, Sanne