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Randomizing events

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  • Randomizing events

    This is my first experiment with SuperLab, and I am unsure how to use it to maximum effect.

    I have an experiment where a trial comprises a product and price. Each product has 4 different prices associated with it, but only one of those prices is shown in a given trial. There are 20 products, so a total of 80 trials - each product is shown 4 times, with one of its different prices each time. These four trials with a single subject should not be run consecutively. This is where I have trouble randomizing from the stimulus lists. Basically I need two randomizations: 1. Which object is selected for the trial; 2. Which price is shown for that product.

    So: a) Can I use a single stimulus list of 20 products, then 20 stimulus lists of 4 prices (one list for each product), when I do not want all 4 prices of a single product shown consecutively (unless by chance)? Each product will appear 4 times, but randomly through the experiment. If I define the product as a trial, then price as the event, I think it will run through all for 4 prices once it has chosen a product. I do not want this.
    b) With half the objects I want to show the product first, and with the other half, show the price first. If the price is shown first, the product must still have been selected a priori, since each product has a different set of 4 prices. For the price-first scenario, can I get SuperLab to select the product, then the price, but show the price first?

    As a further complication, I want to run exactly the same experiment with 5 different subjects. Can I save the selection order made with the first subject, and repeat it exactly with 4 others, then do a new order with 5 more, etc.

    Thanks for your time and help.

  • #2
    We are working on a sample experiment. It should be posted in the next day or two.


    • #3
      The sample experiment attached uses 3 products and 4 prices. There are tracing events in the experiment to check that the codes are working correctly. Feel free to delete these.

      A code was created named "Last Product Presented". There are as many code levels as there are products. In this case we have Product 1, 2, and 3.

      Block Level
      • Three macros were created, one for each product
      • For each Expression SuperLab is "using only the last 1 trials in the block and Trials marked with code "Last Product Presented" equal to "Product 1, 2 or 3"
      • Under the If True tab it needs to state "Change value of code "Last Product Presented" to "Product 1, 2 or 3" in all trials in this block"

      Trial Level
      • An expression is created for each product. The conditional expression needs to be created for the "Current trial's code "Last Product Presented" is not set to Product 1, 2, or 3"

      Event Level
      • An event needs to be created for each product
      • A stimulus list is used for the prices
      • Feedback is needed for every product event. It provides feedback, Always, at the end of the event, to "Change value of code "Last Product Presented" to "product 1, 2, or 3"
      Attached Files