[R-sig-ME] Logistic modelling with guessing parameter

[Peter Harrison]

Thanks for the suggestion - mafc.cauchit  seems to work with p_ID and audio_name as random effects, but unfortunately not with audio_name as a fixed effect, as I'd hoped for ("cannot generate feasible simplex"). Oh well! 

-----Original Message-----
From: R-sig-mixed-models [mailto:r-sig-mixed-models-bounces at r-project.org] On Behalf Of ken knoblauch
Sent: 08 May 2015 15:29
To: r-sig-mixed-models at r-project.org
Subject: Re: [R-sig-ME] Logistic modelling with guessing parameter

Peter Harrison <pharr011 at ...> writes:

> 
> Hello Ben and Ken,
> 
> Thanks very much for your useful responses!
> 
> Ben - thanks for your hint re non-finite values in PIRLS, I'll bear 
> that
in mind for the future. I added
> non-finite warning checks to the link functions etc. and nothing
came up this time, unfortunately.
> 
> You're right, all of the groups show complete separation - I hadn't
thought too carefully about this but
> realise now that it will be a problem. I think I might have to merge 
> the
 musical tracks into larger groups,
> perhaps by metre, genre, etc.
> 
> Thanks a lot for the great graph, too!
> 
> Ken - thanks for the heads-up about using the link directly from
the psyphy package, that definitely
> simplifies things! Sorry, the code I gave and you ran is
an example that does work: responses ~ accuracy +
> (1|p_ID). The model I was having problems with
was when I added the "audio_name" predictor, i.e.
> responses ~ accuracy + audio_name + (1|p_ID).

Something that you can try is the mafc.cauchit link that would impose a less steep slope because of the heavy tails of the Cauchy. This might be less sensitive to complete separation sort of like a regularization of the psychometric function slope.
I have used this link to correct for the bias introduced by lapses at the upper asymptote instead of introducing a lapse parameter which is not obvious how to do otherwise with glmer. 


> 
> Best wishes,
> Peter
> 
> 	[[alternative HTML version deleted]]
> 
>

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