[R-lang] Re: High collinearity in logit linear mixed effects modelling

[Zhenguang Cai]

Dear Professor Trueswell,

Thanks for the advice. I did that and found that P2 can be subsumed by 
P1 but not the other way round. I think that means something.

My further question is that we always at least have to determine 1) 
whether P2 can be subsumed by P1 (i.e., whether the addition of P2 can 
significantly improve model fit) and 2) whether P2 can be subsumed by P1 
(i.e., whether the addition of P2 can significantly improve model fit). 
Is that correct?

Zhenguang

John Trueswell wrote:
> Zhenguang,
> 
> If Experiment 1 and Experiment 2 are similar enough, you could combine
> the data from the two experiments and model the entire set (keeping
> Experiment as a predictor in the model, to see if that matters).
> 
> John Trueswell
> 
> 
> On Thu, Jun 24, 2010 at 5:17 PM, Zhenguang Cai <s0782345@sms.ed.ac.uk> wrote:
>> Dear R-language people,
>>
>> I realized that this is probably a question that has been frequently asked
>> already, so sorry for spam to some people.
>>
>> I found high correlation between two predictors (P1 and P2) (r  = .8). So
>> following Florian's advice, I did model comparisons to try to exclude one of
>> the predictors. However, I am not sure whether I did things in the right
>> way.
>>
>> Step 1 (to determine whether P2 can be subsumed by P1)
>>
>> M0<- lmer(Data~1+(1|Subject)+(1|Item),family='binomial')
>> M1<- lmer(Data~P1+(1|Subject)+(1|Item),family='binomial')
>> M2 <- lmer(Data~P1+P2+(1|Subject)+(1|Item),family='binomial')
>>
>> anova (M0, M1)
>> anova (M1, M2)
>>
>>
>> Step 1 (to determine whether P1 can be subsumed by P2)
>>
>> M0<- lmer(Data~1+(1|Subject)+(1|Item),family='binomial')
>> M1<- lmer(Data~P2+(1|Subject)+(1|Item),family='binomial')
>> M2 <- lmer(Data~P2+P1+(1|Subject)+(1|Item),family='binomial')
>>
>> anova (M0, M1)
>> anova (M1, M2)
>>
>>
>> In Experiment 1, I found P2 can be subsumed by P1 but not the other way
>> round.
>>
>> However, in Experiment 2, I found P1 and P2 can be subsumed by each other.
>> How to resolve this?
>>
>>
>> Thanks,
>>
>> Zhenguang
>>
>> --
>> The University of Edinburgh is a charitable body, registered in
>> Scotland, with registration number SC005336.
>>
>>
> 

-- 
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.