Working Memory Task

[Zeliha Seyidoğlu]

Hi, I'm designing a working memory task that includes six boxes and randomly selected letters in four of the boxes. I have 15 different placement possibilities. It should show a random placement of four random letters. However, it gives only random placement. It gives a few random placements for a set of four letters but repeats the same letters in every placement possibility. How can I fix this?