# How to pick up just few trials from stimuli list and present it randomly?

I have a trials, which using larger stimuli list but I want to present only few of them, randomly selected and in random order…

In details: I have trial which contains given sequence of events - e.g. ABC, and each events contains a list of stimli from A1 to A10, B1 - B10 and so on. Another trial contains different order of events e.g. BCA, but again each event contain a list of stimuli.

Now, I would like to randomly pick up only 2 from 10 possible trials in each order (so, only 2 from the order ABC, and 2 form BCA) and present it randomly within a block… is it possible?

What I did for now is to create a block which contain a two trials (ABC and BCA) and made a macro to randomly select 4 trials, but I’m unable to make it counterbalanced (what SL does is selecting 4 trails from 20 possible ABC/BCA, but not 2 from ABC and 2 from BCA)… Another way I invented was to create two blocks separetly for ABC and BCA, but then the trials are not presented in random order (so first it goes with two trials randomly chosen from ABC and then 2 from BCA)

Is there any other way to do it?

There is a way to do this. Please see below.

Create a code named "Trial Sequence" with two value "ABC" and "BCA"
• Mark the "ABC" and "BCA" trials with corresponding code values
• Create another code "Presented 2 ABC trials" with the values" "Yes" and "No"
• Do the same with "Presented 2 BCA trials" with the values "Yes" and "No"
• You will need a macro that states: If number of trials presented with "Trial Sequence" code set to "ABC", then use action: "Change Code Values for all Trials" presented 2 ABC trials set to "Yes"
• You will do the same for "BCA"
• At the trial level, under the "When to Present" tab, "Current Trial's Code Value" "Presented 2 ABC trials" is set to "No"
• Same for the other "BCA" trial

OK, thx… it seems to work, but it’s rather complicated to set it if there are lot of possible orders…

As a matter of fact I’ll have 24 of them - so 24 different types of trials, and each contain 10 lists - so all together there are 240 possible trials, while I want to present only 48 and have it counterbalanced between the different types of trials… Which means I have to prepare 24 different codes, match them precisely and then prepare another 24 macros (with precisely described rules)… I hope I won’t made a mistake.

I would gratefully welcome possibility to set the macro with simple rule “present the trial only “number” of times for each participant” or something like that.

I will pass your feedback to the development team, thank you.