Reply To: Choosing subet of items to present

PennController for IBEX Forums Support Choosing subet of items to present Reply To: Choosing subet of items to present


Hi Ana,

I’m not sure what you have in mind about the pick function but I doubt it would be very helpful. Any group manipulation is most straightforwardly handled using the Group/List column. Using the pick function to assign different trials to different participants would require accessing the internal counter and using plain javascript conditional logic to execute different pick functions depending on the counter value. Which would eventually just reproduce the Group/List behavior. You use pick to select the first N trials from a set, for example pick(randomize("experiment"), 5) will pick the first five trials from the randomized set of all trials labeled “experiment” that were generated by your script

If you want your participants to see repetitions of the same condition, I’d say it’s something you need to consider ahead of the actual implementation of your experiment: say you have a factor with 2 levels, you want a latin-square design, and you want each participant to see 2 repetitions of each condition. If you don’t want a participant to see the same item multiple times in two different conditions within the same experiment, you will need to have at least 4 different items: your participants will see the first 2 items in a different condition each, and same thing for the last 2 items, making for a total of 2 items per condition. Which means you will need to define 4 items*2 conditions = 8 item-variants. With some designs you can define derive the two conditions from an algorithm, so if equipped with such an algorithm, the minimal amount of information you would ultimately need to hard-code would be the two main items. But most of the time you need to manually define the specifics of each condition for each main item. For example, items 1 and 2 might consist of two completely different sentences, and the two conditions might vary names and pronouns: unless those name/pronoun variations are completely deterministic, you still need to list the 8 variants. Then, just use a Group/List column to make sure you have a latin-square design with repetition. Here’s an example:

1,Philip,himself,Philip thinks about himself a lot,A
1,Ana,herself,Ana thinks about herself a lot,B
2,Gregory,himself,Gregory rarely talks about himself,B
2,Susan,herself,Susan rarely talks about herself,A
3,Peter,himself,Peter gives himself too much credit,A
3,Melody,herself,Melody gives herself too much credit,B
4,Harry,himself,Harry introduces himself as an entrepreneur,B
4,Shelly,herself,Shelly introduces herself as an entrepreneur,A

Here I need to list all eight proper names to define the 8 variants resulting from crossing the two conditions with the four items. Each sentence is different, so the 8 variants could not be generated from a table with fewer rows. Each participants will see two repetitions of each condition: for example, participants in group A will see items 1 and 3 in the masculine-grammatical-gender condition, and items 2 and 4 in the feminine-grammatical-gender condition

I hope my explanations were clear enough. Let me know if you have questions