[R-sig-ME] Extremely High Slope/Intercept Correlation

[Viechtbauer Wolfgang (STAT)]

I assume 'Male' is dichotomous, so it has just two levels. Not likely that one can estimate any variance components based on that grouping variable with any degree of precision.

> -----Original Message-----
> From: r-sig-mixed-models-bounces at r-project.org [mailto:r-sig-mixed-models-
> bounces at r-project.org] On Behalf Of ONKELINX, Thierry
> Sent: Monday, December 02, 2013 10:20
> To: AvianResearchDivision; r-sig-mixed-models at r-project.org
> Subject: Re: [R-sig-ME] Extremely High Slope/Intercept Correlation
> 
> This can be caused by having more complexity than the data allows. Note
> that the variance of the random slope is small.
> 
> -----Oorspronkelijk bericht-----
> Van: r-sig-mixed-models-bounces at r-project.org [mailto:r-sig-mixed-models-
> bounces at r-project.org] Namens AvianResearchDivision
> Verzonden: maandag 2 december 2013 2:05
> Aan: r-sig-mixed-models at r-project.org
> Onderwerp: [R-sig-ME] Extremely High Slope/Intercept Correlation
> 
> Hi all,
> 
> I came across extremely high slope/intercept correlation (-1.00) when
> running the following model:
> 
> model<-lmer(X~Y+(Y|Male))
> 
> summary(model)
> 
> Random effects:
> 
>  Groups             Name               Variance          Std.Dev.
> Corr
> 
> 
>  Male                (Intercept)          1.562e-01        0.3952284
> 
>                         Y                       7.581e-07       0.0008707
> -1.00
> 
>                         Residual            2.661e-01        0.5158953
> 
> Number of obs: 879, groups: Male, 59
> 
> 
> What is causing this?  This high of a correlation does not seem possible,
> especially in ecology.  Any suggestions moving forward?
> 
> 
> Thank you,
> 
> Jacob
> 
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