Problem with per-trial weight adjustment using setweight

[LaurensK90]

You mentioned not to use SetWeight while the list is running... but that's 
actually exactly what I've been doing. I received a reply from PST support 
saying that this was impossible, but after following your suggestion of 
adding List.Reset, the switch ratio works exactly as intended. They also 
sent me an example design (attached) using multiple lists with different 
weights, like you suggested, but since this is not able to make a trial 
selection based on the previous trial, it results in a switch ratio of 
1:3.5 instead of 1:3. I know how to solve this, but again, it involves 
using SetWeight to set the weight of the inappropriate list to zero while 
it's running. 
 
Does List.Reset have especially disruptive effects on timing, or does 
running it on every trial have other negative effects I'm not aware of? I 
can see why this method is a bit unorthodox, but since it works, I feel 
like I need a very good reason not to use it.
 
The cheap solution is probably a good option, but I'd still like to 
understand why this is so difficult.

On Tuesday, April 1, 2014 4:58:48 PM UTC+2, McFarlane, David wrote:

> Well...  Implementing specific constraints on randomization at 
> runtime gets very tricky, try searching for discussions using terms 
> such as "random", "pseudorandom", "pseudo-random", "constrain", and 
> "constraint".  Offhand, I feel very leery of any approach using 
> List.SetWeight, and I especially hope that you do not try that while 
> the List itself is running! 
>
> PST shows one time-honored (though crude) method for implementing 
> on-the-fly randomization with contstraints in their "No Repeats on 
> Consecutive Trials" examples on their website, and you might adapt 
> that approach for your program.  That method, however, is a sort of 
> nondeterministic "bogosort" (look that up on Wikipedia) which suffers 
> several problems. 
>
> The cheap answer, which you will find in other discussions, is just 
> to randomize everything before runtime outside of E-Prime.  Construct 
> a "random" sequence that has the properties you seek, then implement 
> that as a Sequential List in E-Prime.  If you want different random 
> orders for different subjects, then construct a few more sequences 
> outside of E-Prime, implement each of your sequences as a nested List 
> (running in Sequential order), and then have E-Prime pick one of 
> those nested Lists on each run (perhaps using a main List set to 
> Counterbalance order).  Or, generate your sequence outside of E-Prime 
> as a properly formatted .txt or .xml file, and then use List 
> LoadMethod "File" to read in the sequence at runtime. 
>
> -- David McFarlane 
>
>
> At 4/1/2014 08:10 AM Tuesday, LaurensK90 wrote: 
> >Now that I have access to E-Basic help again I see that I was 
> >mistaken about the function of List.Reset, and appending this to the 
> >end of the script caused the experiment to create the appropriate 
> >switch ratio. So thank you very much for that suggestion! 
> > 
> >However, my attempt at preventing the experiment from running more 
> >than five consecutive trials of the same type is still not 
> >effective. I suspect there's something wrong with the way I'm trying 
> >to increment the counter variable, which leads to the second If 
> >statement never getting triggered. Could that be the problem? 
>
>

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