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

[T. Florian Jaeger]

Dear Zhenguang,

what do your mean by Experiment 1 and 2? You have two different data sets?

Florian

On Fri, Jun 25, 2010 at 9:12 AM, Zhenguang Cai <s0782345@sms.ed.ac.uk>wrote:

> 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.
>
>
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