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

[ONKELINX, Thierry]

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 op r-project.org [mailto:r-sig-mixed-models-bounces op r-project.org] Namens AvianResearchDivision
Verzonden: maandag 2 december 2013 2:05
Aan: r-sig-mixed-models op 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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