R 和 SPSS 返回不同的參數以進行對數線性分析

Question

我在 R 中對以下研究生招生數據進行了對數線性分析。

grad_admissions <- array(data = c(39, 10, 20, 15, 11, 41, 6, 60), 
                         dim = c(2,2,2), 
                         dimnames = list("department" = c("one","two"),
                                         "gender" = c("male","female"),
                                         "admission" = c("admitted","notadmitted")))

ftable(grad_admissions, row.vars = c("department"),col.vars = c("admission","gender"))

grad_admissions.df <- as.data.frame(as.table(grad_admissions))

grad_admissions.df$gender <- factor(grad_admissions.df$gender, levels = c("female","male"))
grad_admissions.df$department <- factor(grad_admissions.df$department, levels = c("two","one"))
grad_admissions.df$admission <- factor(grad_admissions.df$admission, levels = c("admitted","notadmitted"))


mod1 <- glm(Freq ~ department * gender * admission, 
            data = grad_admissions.df, family = poisson)

summary(mod1)

我還在同一數據集（ 此處為 SAV 文件）上運行了以下 SPSS 語法。

DATASET ACTIVATE DataSet2.
WEIGHT BY Count.

GENLOG Gender Admitted Department
  /MODEL=POISSON
  /PRINT=FREQ RESID ADJRESID ZRESID DEV ESTIM CORR COV
  /PLOT=NONE
  /CRITERIA=CIN(95) ITERATE(20) CONVERGE(0.001) DELTA(.5).

參數估計值如下。 它們相似但不完全相同。 在 SPSS output 中，男性編碼為 0，女性編碼為 1。

誰能解釋為什么它們不一樣？

Answer 1

嘗試以下操作：

GENLOG Department Gender Admitted
  /MODEL=POISSON
  /PRINT=FREQ RESID ADJRESID ZRESID DEV ESTIM CORR COV
  /PLOT=NONE
  /CRITERIA=CIN(95) ITERATE(20) CONVERGE(0.001) DELTA(0).

請注意CRITERIA子命令上的DELTA(0)規范。 默認情況下，SPSS GENLOG 將飽和 model 中每個細胞的細胞計數添加 5，這是在對數線性模型中處理 0 細胞計數的常用技術。