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Official Journal of the Japan Wood Research Society

Table 11 Final nonlinear mixed-effects model. βA0 -βB2 correspond to the fixed effect regression model (intercept, linear, quadratic trend), the bi-parameter is the corresponding random effects

From: An application of mixed-effects model to evaluate the role of age and size on radial variation in wood specific gravity in teak (Tectona grandis)

Fixed effects

  

Estimate

SE

T

Radii

1

βA0

0.5691

0.03113

18.28**

 

2

βB0

0.5831

0.03113

18.73**

Radii*RRD

1

βA1

0.3652

0.00880

2.30*

 

2

βB1

0.3114

0.00880

1.97

Radii*RRD2

1

βA2

− 0.3112

0.00103

− 0.93

 

2

βB2

− 0.3051

0.00103

− 0.92

Random effects

 Level 2 "Tree"

  

Variance

S.E

Z

  

bi

0.001049

0.001615

0.87

 Level 1 "RRD"

     
 

AR(1)

ρ

0.7481

0.03736

20.02**

 

Residual

eij

0.003884

0.000577

6.73**

  1. AR(1) is the autocorrelation coefficient
  2. SE standard error of estimated parameters, t t-test value, z z-test-value, AR(1) = first-order autoregressive process. * p < 0.05, ** p < 0.01