Hello everybody,

I have a question concerning a Single Category IAT. I have three categories: cat1, cat2, cat3. Two of them are displayed in the left corner, one in the right corner. Words appearing in the centre of the screen are sorted by participants to the three categories by pressing one of two keys. To avoid a lateral bias (if stimulus words are presented in equal frequence, the left key would have to be pressed double as often as the right key, 48:24), we want to control the frequencies of the three categories insofar that 58% (meaning, stimuli of cat1 and cat2 need to be presented 21 times each) of the 72 keypresses have to be left, and 42% (30 presentations of words of cat3) right. How can I do that?

Attached you can find the script so far.

Thank you very much in advance!
M.

You need to enter your trials in the right proportions into the noreplace() pools in your <block> elements' /trials attributes.

/ trials = [1-72 = noreplace(Inklleft, Positiv, Negativ)]

will sample the three trials in equal proportions (1:1:1). Adjust the proportions according to your needs by entering unequal amounts of the respective trials into the pool.

A simple example:

/ trials = [1-12 = noreplace(a, b, c)]

will result in 4 a-trials, 4 b-trials, and 4 c-trials in random order. Equal proportions, 1:1:1.

/ trials = [1-12 = noreplace(a, a, b, c)]

will result in twice as many a-trials compared to b- and c-trials, i.e. there'll be 6 a-trials, 3 b-trials, and 3 c-trials; 2:1:1.