解释广义线性混合模型 (GLMM) 中的独立分类变量

Interpreting independent categorical variable in a generalized linear mixed model (GLMM)

我使用具有准泊松回归的广义线性混合模型 (GLMM),并使用惩罚拟似然法(即 glmmPQL)用多元正态随机效应拟合模型。输出结果如下:

收入变量有 3 类,低收入、中低收入、中高收入。在输出中,低收入似乎是参考类别,但我不知道我应该如何解释和报告它。

非常感谢您。

 Linear mixed-effects model fit by maximum likelihood
 Data: my_scaled_data 
 AIC BIC logLik
 NA  NA     NA

 Random effects:
 Formula: ~1 | country
    (Intercept) Residual
 StdDev:    1.191246 7.062197

 Variance function:
 Structure: fixed weights
 Formula: ~invwt 
 Fixed effects:  protests ~ stringency + cpi + income 
                              Value Std.Error  DF   t-value p-value
(Intercept)                3.993691 0.3732307 428 10.700329  0.0000
stringency                 0.152788 0.0322449 428  4.738373  0.0000
cpi                       -0.509498 0.3093523 428 -1.646984  0.1003
incomelower middle income -0.028550 0.2156300 428 -0.132403  0.8947
incomeupper middle income -0.528267 0.2520429 428 -2.095941  0.0367
 Correlation: 
                          (Intr) strngn cpi    incmlmi
stringency                -0.005                      
cpi                        0.065 -0.311               
incomelower middle income -0.302 -0.089  0.056        
incomeupper middle income -0.244 -0.060 -0.004  0.539 

Standardized Within-Group Residuals:
       Min         Q1        Med         Q3        Max 
-1.6874331 -0.4638920 -0.1344516  0.2557120 10.2539363 

Number of Observations: 444
Number of Groups: 12 

Income variable has 3 categories, low income, lower middle income, upper middle income. In the output, low income appears to be reference category but I don't know how should I interpret and report this.

这是处理分类回归变量的常规方法。每个估计都被解释为与参考水平的对比。因此,incomelower middle income 的线性预测变量比参考水平低 0.028550,incomeupper middle income 的线性预测变量比参考水平低 0.528267。