Randomization condition

Coding
1

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

3

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.

4

Dear SDAMcIntyre,

mm thank you, that make sense… 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