Hot to make RWG with the constraint of equal numbers of stimuli of each type?

[Giorgos P. Argyropoulos]

Thanks very much, I think it does, will try it and let you know,

Cheers!

Giorgos

[Giorgos P. Argyropoulos]

Hi there, sorry to bother you again, but I seem to have mislead you with the description of the stimuli: You see, I have 30 stimuli of four different versions each, but my constraint is not that I have to have every single version of each of the 30 stimuli occurring, but, quite on the contrary actually, that:

- only one version (a,b,c,d) out of four is selected out of each of the 30 stimuli
- in the end, I should have an equal number of a's with b's, c's, and d's.

What you have suggested that I should do makes the all four versions of each of the 30 stimuli appear, that's why I'm saying I wasn't clear enough (profuse apologies for that).

Thanks a mill for your patience and time

Giorgos

[jarvis24]

Not sure what you mean by:

one version (a,b,c,d) out of four is selected out of each of the 30 stimuli

Do you mean that you have 30 a's, 30 b's, 30 c's and 30 d's? And that you want to pick one from each so that you have a set of 4? And then that you want to do this over and over again (10 times? 30 times?) so that the subject is given multiple sets like this? And is the order within each chosen set also to be random (e.g., adcb, bcad, etc.)?

[Giorgos P. Argyropoulos]

Hi,

thanks for your time on this.

So, basically, I have:

1a, 1b, 1c, 1d
2a, 2b, 2c, 2d
....................
40a, 40b, 40c, 40d

Now, for each number (i.e., 1, 2, etc) I want for each session to randomly pick out only one version (a,b,c,d) for each number. So, if 1a appears, I don't want any 1b,1c, or 1d appear. Plus, in the end, I want to have for each session 10 a's, 10 b's 10 c's and 10 d's. But no stimulus appearing in more than one version in one session either. Does that help at all?

Thanks so much

Giorgos

[Giorgos P. Argyropoulos]

So, yes, the order would ideally differ as well, I don't need it to be fixed at all.

Cheers

G.

[Giorgos P. Argyropoulos]

And ideally I want each subject to see a total of 40 stimuli, different version (b instead of a), and different order (stimulus "3" in the place of stimulus "1") for each subject....

Cheers

G.

[jarvis24]

So you want to control the pattern of randomization across subjects? So, e.g., if you have 100 subjects, then 25 will have seen 1a, 25 will have seen 1b, 25 will have seen 1c and 25 will have seen 1d?